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2.1J: Hydrogen Bonding and Van der Waals Forces - Biology

2.1J: Hydrogen Bonding and Van der Waals Forces - Biology


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Hydrogen bonds and van der Waals interactions are two types of weak bonds that are necessary to the basic building blocks of life.

Learning Objectives

  • Describe how hydrogen bonds and van der Waals interactions occur

Key Points

  • Hydrogen bonds provide many of the critical, life-sustaining properties of water and also stabilize the structures of proteins and DNA, the building block of cells.
  • Hydrogen bonds occur in inorganic molecules, such as water, and organic molecules, such as DNA and proteins.
  • Van der Waals attractions can occur between any two or more molecules and are dependent on slight fluctuations of the electron densities.
  • While hydrogen bonds and van der Waals interactions are weak individually, they are strong combined in vast numbers.

Key Terms

  • van der Waals interactions: A weak force of attraction between electrically neutral molecules that collide with or pass very close to each other. The van der Waals force is caused by temporary attractions between electron-rich regions of one molecule and electron-poor regions of another.
  • electronegativity: The tendency of an atom or molecule to draw electrons towards itself, form dipoles, and thus form bonds.
  • hydrogen bond: The attraction between a partially positively-charged hydrogen atom attached to a highly electronegative atom (such as nitrogen, oxygen, or fluorine) and another nearby electronegative atom.

Ionic and covalent bonds between elements require energy to break. Ionic bonds are not as strong as covalent, which determines their behavior in biological systems. However, not all bonds are ionic or covalent bonds. Weaker bonds can also form between molecules. Two weak bonds that occur frequently are hydrogen bonds and van der Waals interactions.

Hydrogen Bonding

Hydrogen bonds provide many of the critical, life-sustaining properties of water and also stabilize the structures of proteins and DNA, the building block of cells. When polar covalent bonds containing hydrogen form, the hydrogen in that bond has a slightly positive charge because hydrogen’s one electron is pulled more strongly toward the other element and away from the hydrogen. Because the hydrogen is slightly positive, it will be attracted to neighboring negative charges. When this happens, an interaction occurs between the δ+of the hydrogen from one molecule and the δ– charge on the more electronegative atoms of another molecule, usually oxygen or nitrogen, or within the same molecule. This interaction is called a hydrogen bond. This type of bond is common and occurs regularly between water molecules. Individual hydrogen bonds are weak and easily broken; however, they occur in very large numbers in water and in organic polymers, creating a major force in combination. Hydrogen bonds are also responsible for zipping together the DNA double helix.

Applications for Hydrogen Bonds

Hydrogen bonds occur in inorganic molecules, such as water, and organic molecules, such as DNA and proteins. The two complementary strands of DNA are held together by hydrogen bonds between complementary nucleotides (A&T, C&G). Hydrogen bonding in water contributes to its unique properties, including its high boiling point (100 °C) and surface tension.

In biology, intramolecular hydrogen bonding is partly responsible for the secondary, tertiary, and quaternary structures of proteins and nucleic acids. The hydrogen bonds help the proteins and nucleic acids form and maintain specific shapes.

Van der Waals Interactions

Like hydrogen bonds, van der Waals interactions are weak attractions or interactions between molecules. Van der Waals attractions can occur between any two or more molecules and are dependent on slight fluctuations of the electron densities, which are not always symmetrical around an atom. For these attractions to happen, the molecules need to be very close to one another. These bonds—along with ionic, covalent, and hydrogen bonds—contribute to the three-dimensional structure of proteins that is necessary for their proper function.

Van der Waals attraction: Explore how Van der Waals attractions and temperature affect intermolecular interactions.


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Contents

The word chemistry comes from a modification of the word alchemy, which referred to an earlier set of practices that encompassed elements of chemistry, metallurgy, philosophy, astrology, astronomy, mysticism and medicine. Alchemy is often seen as linked to the quest to turn lead or other base metals into gold, though alchemists were also interested in many of the questions of modern chemistry. [8]

The modern word alchemy in turn is derived from the Arabic word al-kīmīā (الكیمیاء). This may have Egyptian origins since al-kīmīā is derived from the Greek χημία, which is in turn derived from the word Kemet, which is the ancient name of Egypt in the Egyptian language. [9] Alternately, al-kīmīā may derive from χημεία, meaning "cast together". [10]

The current model of atomic structure is the quantum mechanical model. [11] Traditional chemistry starts with the study of elementary particles, atoms, molecules, [12] substances, metals, crystals and other aggregates of matter. Matter can be studied in solid, liquid, gas and plasma states, in isolation or in combination. The interactions, reactions and transformations that are studied in chemistry are usually the result of interactions between atoms, leading to rearrangements of the chemical bonds which hold atoms together. Such behaviors are studied in a chemistry laboratory.

The chemistry laboratory stereotypically uses various forms of laboratory glassware. However glassware is not central to chemistry, and a great deal of experimental (as well as applied/industrial) chemistry is done without it.

A chemical reaction is a transformation of some substances into one or more different substances. [13] The basis of such a chemical transformation is the rearrangement of electrons in the chemical bonds between atoms. It can be symbolically depicted through a chemical equation, which usually involves atoms as subjects. The number of atoms on the left and the right in the equation for a chemical transformation is equal. (When the number of atoms on either side is unequal, the transformation is referred to as a nuclear reaction or radioactive decay.) The type of chemical reactions a substance may undergo and the energy changes that may accompany it are constrained by certain basic rules, known as chemical laws.

Energy and entropy considerations are invariably important in almost all chemical studies. Chemical substances are classified in terms of their structure, phase, as well as their chemical compositions. They can be analyzed using the tools of chemical analysis, e.g. spectroscopy and chromatography. Scientists engaged in chemical research are known as chemists. [14] Most chemists specialize in one or more sub-disciplines. Several concepts are essential for the study of chemistry some of them are: [15]

Matter

In chemistry, matter is defined as anything that has rest mass and volume (it takes up space) and is made up of particles. The particles that make up matter have rest mass as well – not all particles have rest mass, such as the photon. Matter can be a pure chemical substance or a mixture of substances. [16]

The atom is the basic unit of chemistry. It consists of a dense core called the atomic nucleus surrounded by a space occupied by an electron cloud. The nucleus is made up of positively charged protons and uncharged neutrons (together called nucleons), while the electron cloud consists of negatively charged electrons which orbit the nucleus. In a neutral atom, the negatively charged electrons balance out the positive charge of the protons. The nucleus is dense the mass of a nucleon is approximately 1,836 times that of an electron, yet the radius of an atom is about 10,000 times that of its nucleus. [17] [18]

The atom is also the smallest entity that can be envisaged to retain the chemical properties of the element, such as electronegativity, ionization potential, preferred oxidation state(s), coordination number, and preferred types of bonds to form (e.g., metallic, ionic, covalent).

Element

A chemical element is a pure substance which is composed of a single type of atom, characterized by its particular number of protons in the nuclei of its atoms, known as the atomic number and represented by the symbol Z. The mass number is the sum of the number of protons and neutrons in a nucleus. Although all the nuclei of all atoms belonging to one element will have the same atomic number, they may not necessarily have the same mass number atoms of an element which have different mass numbers are known as isotopes. For example, all atoms with 6 protons in their nuclei are atoms of the chemical element carbon, but atoms of carbon may have mass numbers of 12 or 13. [18]

The standard presentation of the chemical elements is in the periodic table, which orders elements by atomic number. The periodic table is arranged in groups, or columns, and periods, or rows. The periodic table is useful in identifying periodic trends. [19]

Compound

A compound is a pure chemical substance composed of more than one element. The properties of a compound bear little similarity to those of its elements. [20] The standard nomenclature of compounds is set by the International Union of Pure and Applied Chemistry (IUPAC). Organic compounds are named according to the organic nomenclature system. [21] The names for inorganic compounds are created according to the inorganic nomenclature system. When a compound has more than one component, then they are divided into two classes, the electropositive and the electronegative components. [22] In addition the Chemical Abstracts Service has devised a method to index chemical substances. In this scheme each chemical substance is identifiable by a number known as its CAS registry number.

Molecule

A molecule is the smallest indivisible portion of a pure chemical substance that has its unique set of chemical properties, that is, its potential to undergo a certain set of chemical reactions with other substances. However, this definition only works well for substances that are composed of molecules, which is not true of many substances (see below). Molecules are typically a set of atoms bound together by covalent bonds, such that the structure is electrically neutral and all valence electrons are paired with other electrons either in bonds or in lone pairs.

Thus, molecules exist as electrically neutral units, unlike ions. When this rule is broken, giving the "molecule" a charge, the result is sometimes named a molecular ion or a polyatomic ion. However, the discrete and separate nature of the molecular concept usually requires that molecular ions be present only in well-separated form, such as a directed beam in a vacuum in a mass spectrometer. Charged polyatomic collections residing in solids (for example, common sulfate or nitrate ions) are generally not considered "molecules" in chemistry. Some molecules contain one or more unpaired electrons, creating radicals. Most radicals are comparatively reactive, but some, such as nitric oxide (NO) can be stable.

The "inert" or noble gas elements (helium, neon, argon, krypton, xenon and radon) are composed of lone atoms as their smallest discrete unit, but the other isolated chemical elements consist of either molecules or networks of atoms bonded to each other in some way. Identifiable molecules compose familiar substances such as water, air, and many organic compounds like alcohol, sugar, gasoline, and the various pharmaceuticals.

However, not all substances or chemical compounds consist of discrete molecules, and indeed most of the solid substances that make up the solid crust, mantle, and core of the Earth are chemical compounds without molecules. These other types of substances, such as ionic compounds and network solids, are organized in such a way as to lack the existence of identifiable molecules per se. Instead, these substances are discussed in terms of formula units or unit cells as the smallest repeating structure within the substance. Examples of such substances are mineral salts (such as table salt), solids like carbon and diamond, metals, and familiar silica and silicate minerals such as quartz and granite.

One of the main characteristics of a molecule is its geometry often called its structure. While the structure of diatomic, triatomic or tetra-atomic molecules may be trivial, (linear, angular pyramidal etc.) the structure of polyatomic molecules, that are constituted of more than six atoms (of several elements) can be crucial for its chemical nature.

Substance and mixture

Examples of pure chemical substances. From left to right: the elements tin (Sn) and sulfur (S), diamond (an allotrope of carbon), sucrose (pure sugar), and sodium chloride (salt) and sodium bicarbonate (baking soda), which are both ionic compounds.

A chemical substance is a kind of matter with a definite composition and set of properties. [23] A collection of substances is called a mixture. Examples of mixtures are air and alloys. [24]

Mole and amount of substance

The mole is a unit of measurement that denotes an amount of substance (also called chemical amount). One mole is defined to contain exactly 6.022 140 76 × 10 23 particles (atoms, molecules, ions, or electrons), where the number of particles per mole is known as the Avogadro constant. [25] Molar concentration is the amount of a particular substance per volume of solution, and is commonly reported in mol/dm 3 . [26]

Phase

In addition to the specific chemical properties that distinguish different chemical classifications, chemicals can exist in several phases. For the most part, the chemical classifications are independent of these bulk phase classifications however, some more exotic phases are incompatible with certain chemical properties. A phase is a set of states of a chemical system that have similar bulk structural properties, over a range of conditions, such as pressure or temperature.

Physical properties, such as density and refractive index tend to fall within values characteristic of the phase. The phase of matter is defined by the phase transition, which is when energy put into or taken out of the system goes into rearranging the structure of the system, instead of changing the bulk conditions.

Sometimes the distinction between phases can be continuous instead of having a discrete boundary' in this case the matter is considered to be in a supercritical state. When three states meet based on the conditions, it is known as a triple point and since this is invariant, it is a convenient way to define a set of conditions.

The most familiar examples of phases are solids, liquids, and gases. Many substances exhibit multiple solid phases. For example, there are three phases of solid iron (alpha, gamma, and delta) that vary based on temperature and pressure. A principal difference between solid phases is the crystal structure, or arrangement, of the atoms. Another phase commonly encountered in the study of chemistry is the aqueous phase, which is the state of substances dissolved in aqueous solution (that is, in water).

Less familiar phases include plasmas, Bose–Einstein condensates and fermionic condensates and the paramagnetic and ferromagnetic phases of magnetic materials. While most familiar phases deal with three-dimensional systems, it is also possible to define analogs in two-dimensional systems, which has received attention for its relevance to systems in biology.

Bonding

Atoms sticking together in molecules or crystals are said to be bonded with one another. A chemical bond may be visualized as the multipole balance between the positive charges in the nuclei and the negative charges oscillating about them. [27] More than simple attraction and repulsion, the energies and distributions characterize the availability of an electron to bond to another atom.

A chemical bond can be a covalent bond, an ionic bond, a hydrogen bond or just because of Van der Waals force. Each of these kinds of bonds is ascribed to some potential. These potentials create the interactions which hold atoms together in molecules or crystals. In many simple compounds, valence bond theory, the Valence Shell Electron Pair Repulsion model (VSEPR), and the concept of oxidation number can be used to explain molecular structure and composition.

An ionic bond is formed when a metal loses one or more of its electrons, becoming a positively charged cation, and the electrons are then gained by the non-metal atom, becoming a negatively charged anion. The two oppositely charged ions attract one another, and the ionic bond is the electrostatic force of attraction between them. For example, sodium (Na), a metal, loses one electron to become an Na + cation while chlorine (Cl), a non-metal, gains this electron to become Cl − . The ions are held together due to electrostatic attraction, and that compound sodium chloride (NaCl), or common table salt, is formed.

In a covalent bond, one or more pairs of valence electrons are shared by two atoms: the resulting electrically neutral group of bonded atoms is termed a molecule. Atoms will share valence electrons in such a way as to create a noble gas electron configuration (eight electrons in their outermost shell) for each atom. Atoms that tend to combine in such a way that they each have eight electrons in their valence shell are said to follow the octet rule. However, some elements like hydrogen and lithium need only two electrons in their outermost shell to attain this stable configuration these atoms are said to follow the duet rule, and in this way they are reaching the electron configuration of the noble gas helium, which has two electrons in its outer shell.

Similarly, theories from classical physics can be used to predict many ionic structures. With more complicated compounds, such as metal complexes, valence bond theory is less applicable and alternative approaches, such as the molecular orbital theory, are generally used. See diagram on electronic orbitals.

Energy

In the context of chemistry, energy is an attribute of a substance as a consequence of its atomic, molecular or aggregate structure. Since a chemical transformation is accompanied by a change in one or more of these kinds of structures, it is invariably accompanied by an increase or decrease of energy of the substances involved. Some energy is transferred between the surroundings and the reactants of the reaction in the form of heat or light thus the products of a reaction may have more or less energy than the reactants.

A reaction is said to be exergonic if the final state is lower on the energy scale than the initial state in the case of endergonic reactions the situation is the reverse. A reaction is said to be exothermic if the reaction releases heat to the surroundings in the case of endothermic reactions, the reaction absorbs heat from the surroundings.

Chemical reactions are invariably not possible unless the reactants surmount an energy barrier known as the activation energy. The speed of a chemical reaction (at given temperature T) is related to the activation energy E, by the Boltzmann's population factor e − E / k T > – that is the probability of a molecule to have energy greater than or equal to E at the given temperature T. This exponential dependence of a reaction rate on temperature is known as the Arrhenius equation. The activation energy necessary for a chemical reaction to occur can be in the form of heat, light, electricity or mechanical force in the form of ultrasound. [28]

A related concept free energy, which also incorporates entropy considerations, is a very useful means for predicting the feasibility of a reaction and determining the state of equilibrium of a chemical reaction, in chemical thermodynamics. A reaction is feasible only if the total change in the Gibbs free energy is negative, Δ G ≤ 0 if it is equal to zero the chemical reaction is said to be at equilibrium.

There exist only limited possible states of energy for electrons, atoms and molecules. These are determined by the rules of quantum mechanics, which require quantization of energy of a bound system. The atoms/molecules in a higher energy state are said to be excited. The molecules/atoms of substance in an excited energy state are often much more reactive that is, more amenable to chemical reactions.

The phase of a substance is invariably determined by its energy and the energy of its surroundings. When the intermolecular forces of a substance are such that the energy of the surroundings is not sufficient to overcome them, it occurs in a more ordered phase like liquid or solid as is the case with water (H2O) a liquid at room temperature because its molecules are bound by hydrogen bonds. [29] Whereas hydrogen sulfide (H2S) is a gas at room temperature and standard pressure, as its molecules are bound by weaker dipole-dipole interactions.

The transfer of energy from one chemical substance to another depends on the size of energy quanta emitted from one substance. However, heat energy is often transferred more easily from almost any substance to another because the phonons responsible for vibrational and rotational energy levels in a substance have much less energy than photons invoked for the electronic energy transfer. Thus, because vibrational and rotational energy levels are more closely spaced than electronic energy levels, heat is more easily transferred between substances relative to light or other forms of electronic energy. For example, ultraviolet electromagnetic radiation is not transferred with as much efficacy from one substance to another as thermal or electrical energy.

The existence of characteristic energy levels for different chemical substances is useful for their identification by the analysis of spectral lines. Different kinds of spectra are often used in chemical spectroscopy, e.g. IR, microwave, NMR, ESR, etc. Spectroscopy is also used to identify the composition of remote objects – like stars and distant galaxies – by analyzing their radiation spectra.

The term chemical energy is often used to indicate the potential of a chemical substance to undergo a transformation through a chemical reaction or to transform other chemical substances.

Reaction

When a chemical substance is transformed as a result of its interaction with another substance or with energy, a chemical reaction is said to have occurred. A chemical reaction is therefore a concept related to the "reaction" of a substance when it comes in close contact with another, whether as a mixture or a solution exposure to some form of energy, or both. It results in some energy exchange between the constituents of the reaction as well as with the system environment, which may be designed vessels—often laboratory glassware.

Chemical reactions can result in the formation or dissociation of molecules, that is, molecules breaking apart to form two or more molecules or rearrangement of atoms within or across molecules. Chemical reactions usually involve the making or breaking of chemical bonds. Oxidation, reduction, dissociation, acid–base neutralization and molecular rearrangement are some of the commonly used kinds of chemical reactions.

A chemical reaction can be symbolically depicted through a chemical equation. While in a non-nuclear chemical reaction the number and kind of atoms on both sides of the equation are equal, for a nuclear reaction this holds true only for the nuclear particles viz. protons and neutrons. [30]

The sequence of steps in which the reorganization of chemical bonds may be taking place in the course of a chemical reaction is called its mechanism. A chemical reaction can be envisioned to take place in a number of steps, each of which may have a different speed. Many reaction intermediates with variable stability can thus be envisaged during the course of a reaction. Reaction mechanisms are proposed to explain the kinetics and the relative product mix of a reaction. Many physical chemists specialize in exploring and proposing the mechanisms of various chemical reactions. Several empirical rules, like the Woodward–Hoffmann rules often come in handy while proposing a mechanism for a chemical reaction.

According to the IUPAC gold book, a chemical reaction is "a process that results in the interconversion of chemical species." [31] Accordingly, a chemical reaction may be an elementary reaction or a stepwise reaction. An additional caveat is made, in that this definition includes cases where the interconversion of conformers is experimentally observable. Such detectable chemical reactions normally involve sets of molecular entities as indicated by this definition, but it is often conceptually convenient to use the term also for changes involving single molecular entities (i.e. 'microscopic chemical events').

Ions and salts

An ion is a charged species, an atom or a molecule, that has lost or gained one or more electrons. When an atom loses an electron and thus has more protons than electrons, the atom is a positively charged ion or cation. When an atom gains an electron and thus has more electrons than protons, the atom is a negatively charged ion or anion. Cations and anions can form a crystalline lattice of neutral salts, such as the Na + and Cl − ions forming sodium chloride, or NaCl. Examples of polyatomic ions that do not split up during acid–base reactions are hydroxide (OH − ) and phosphate (PO4 3− ).

Plasma is composed of gaseous matter that has been completely ionized, usually through high temperature.

Acidity and basicity

A substance can often be classified as an acid or a base. There are several different theories which explain acid–base behavior. The simplest is Arrhenius theory, which states that acid is a substance that produces hydronium ions when it is dissolved in water, and a base is one that produces hydroxide ions when dissolved in water. According to Brønsted–Lowry acid–base theory, acids are substances that donate a positive hydrogen ion to another substance in a chemical reaction by extension, a base is the substance which receives that hydrogen ion.

A third common theory is Lewis acid–base theory, which is based on the formation of new chemical bonds. Lewis theory explains that an acid is a substance which is capable of accepting a pair of electrons from another substance during the process of bond formation, while a base is a substance which can provide a pair of electrons to form a new bond. According to this theory, the crucial things being exchanged are charges. [32] There are several other ways in which a substance may be classified as an acid or a base, as is evident in the history of this concept. [33]

Acid strength is commonly measured by two methods. One measurement, based on the Arrhenius definition of acidity, is pH, which is a measurement of the hydronium ion concentration in a solution, as expressed on a negative logarithmic scale. Thus, solutions that have a low pH have a high hydronium ion concentration and can be said to be more acidic. The other measurement, based on the Brønsted–Lowry definition, is the acid dissociation constant (Ka), which measures the relative ability of a substance to act as an acid under the Brønsted–Lowry definition of an acid. That is, substances with a higher Ka are more likely to donate hydrogen ions in chemical reactions than those with lower Ka values.

Redox

Redox (reduction-oxidation) reactions include all chemical reactions in which atoms have their oxidation state changed by either gaining electrons (reduction) or losing electrons (oxidation). Substances that have the ability to oxidize other substances are said to be oxidative and are known as oxidizing agents, oxidants or oxidizers. An oxidant removes electrons from another substance. Similarly, substances that have the ability to reduce other substances are said to be reductive and are known as reducing agents, reductants, or reducers.

A reductant transfers electrons to another substance and is thus oxidized itself. And because it "donates" electrons it is also called an electron donor. Oxidation and reduction properly refer to a change in oxidation number—the actual transfer of electrons may never occur. Thus, oxidation is better defined as an increase in oxidation number, and reduction as a decrease in oxidation number.

Equilibrium

Although the concept of equilibrium is widely used across sciences, in the context of chemistry, it arises whenever a number of different states of the chemical composition are possible, as for example, in a mixture of several chemical compounds that can react with one another, or when a substance can be present in more than one kind of phase.

A system of chemical substances at equilibrium, even though having an unchanging composition, is most often not static molecules of the substances continue to react with one another thus giving rise to a dynamic equilibrium. Thus the concept describes the state in which the parameters such as chemical composition remain unchanged over time.

Chemical laws

Chemical reactions are governed by certain laws, which have become fundamental concepts in chemistry. Some of them are:

The history of chemistry spans a period from very old times to the present. Since several millennia BC, civilizations were using technologies that would eventually form the basis of the various branches of chemistry. Examples include extracting metals from ores, making pottery and glazes, fermenting beer and wine, extracting chemicals from plants for medicine and perfume, rendering fat into soap, making glass, and making alloys like bronze. Chemistry was preceded by its protoscience, alchemy, which is an intuitive but non-scientific approach to understanding the constituents of matter and their interactions. It was unsuccessful in explaining the nature of matter and its transformations, but, by performing experiments and recording the results, alchemists set the stage for modern chemistry. Chemistry as a body of knowledge distinct from alchemy began to emerge when a clear differentiation was made between them by Robert Boyle in his work The Sceptical Chymist (1661). While both alchemy and chemistry are concerned with matter and its transformations, the crucial difference was given by the scientific method that chemists employed in their work. Chemistry is considered to have become an established science with the work of Antoine Lavoisier, who developed a law of conservation of mass that demanded careful measurement and quantitative observations of chemical phenomena. The history of chemistry is intertwined with the history of thermodynamics, especially through the work of Willard Gibbs. [34]

Definition

The definition of chemistry has changed over time, as new discoveries and theories add to the functionality of the science. The term "chymistry", in the view of noted scientist Robert Boyle in 1661, meant the subject of the material principles of mixed bodies. [35] In 1663, the chemist Christopher Glaser described "chymistry" as a scientific art, by which one learns to dissolve bodies, and draw from them the different substances on their composition, and how to unite them again, and exalt them to a higher perfection. [36]

The 1730 definition of the word "chemistry", as used by Georg Ernst Stahl, meant the art of resolving mixed, compound, or aggregate bodies into their principles and of composing such bodies from those principles. [37] In 1837, Jean-Baptiste Dumas considered the word "chemistry" to refer to the science concerned with the laws and effects of molecular forces. [38] This definition further evolved until, in 1947, it came to mean the science of substances: their structure, their properties, and the reactions that change them into other substances – a characterization accepted by Linus Pauling. [39] More recently, in 1998, Professor Raymond Chang broadened the definition of "chemistry" to mean the study of matter and the changes it undergoes. [40]

Discipline

Early civilizations, such as the Egyptians [41] Babylonians and Indians [42] amassed practical knowledge concerning the arts of metallurgy, pottery and dyes, but didn't develop a systematic theory.

A basic chemical hypothesis first emerged in Classical Greece with the theory of four elements as propounded definitively by Aristotle stating that fire, air, earth and water were the fundamental elements from which everything is formed as a combination. Greek atomism dates back to 440 BC, arising in works by philosophers such as Democritus and Epicurus. In 50 BCE, the Roman philosopher Lucretius expanded upon the theory in his book De rerum natura (On The Nature of Things). [43] [44] Unlike modern concepts of science, Greek atomism was purely philosophical in nature, with little concern for empirical observations and no concern for chemical experiments. [45]

An early form of the idea of conservation of mass is the notion that "Nothing comes from nothing" in Ancient Greek philosophy, which can be found in Empedocles (approx. 4th century BC): "For it is impossible for anything to come to be from what is not, and it cannot be brought about or heard of that what is should be utterly destroyed." [46] and Epicurus (3rd century BC), who, describing the nature of the Universe, wrote that "the totality of things was always such as it is now, and always will be". [47]

In the Hellenistic world the art of alchemy first proliferated, mingling magic and occultism into the study of natural substances with the ultimate goal of transmuting elements into gold and discovering the elixir of eternal life. [48] Work, particularly the development of distillation, continued in the early Byzantine period with the most famous practitioner being the 4th century Greek-Egyptian Zosimos of Panopolis. [49] Alchemy continued to be developed and practised throughout the Arab world after the Muslim conquests, [50] and from there, and from the Byzantine remnants, [51] diffused into medieval and Renaissance Europe through Latin translations.

The development of the modern scientific method was slow and arduous, but an early scientific method for chemistry began emerging among early Muslim chemists, beginning with the 9th century Perso-Arab chemist Jābir ibn Hayyān, popularly known as "the father of chemistry". The Arabic works attributed to him introduced a systematic classification of chemical substances, and provided instructions for deriving an inorganic compound (sal ammoniac or ammonium chloride) from organic substances (such as plants, blood, and hair) by chemical means. [52] Some Arabic Jabirian works (e.g., the "Book of Mercy", and the "Book of Seventy") were later translated into Latin under the Latinized name "Geber", [53] and in 13th-century Europe an anonymous writer, usually referred to as pseudo-Geber, started to produce alchemical and metallurgical writings under this name. [54] Later influential Muslim philosophers, such as Abū al-Rayhān al-Bīrūnī [55] and Avicenna [56] disputed the theories of alchemy, particularly the theory of the transmutation of metals.

Under the influence of the new empirical methods propounded by Sir Francis Bacon and others, a group of chemists at Oxford, Robert Boyle, Robert Hooke and John Mayow began to reshape the old alchemical traditions into a scientific discipline. Boyle in particular is regarded as the founding father of chemistry due to his most important work, the classic chemistry text The Sceptical Chymist where the differentiation is made between the claims of alchemy and the empirical scientific discoveries of the new chemistry. [57] He formulated Boyle's law, rejected the classical "four elements" and proposed a mechanistic alternative of atoms and chemical reactions that could be subject to rigorous experiment. [58]

The theory of phlogiston (a substance at the root of all combustion) was propounded by the German Georg Ernst Stahl in the early 18th century and was only overturned by the end of the century by the French chemist Antoine Lavoisier, the chemical analogue of Newton in physics who did more than any other to establish the new science on proper theoretical footing, by elucidating the principle of conservation of mass and developing a new system of chemical nomenclature used to this day. [60]

Before his work, though, many important discoveries had been made, specifically relating to the nature of 'air' which was discovered to be composed of many different gases. The Scottish chemist Joseph Black (the first experimental chemist) and the Flemish Jan Baptist van Helmont discovered carbon dioxide, or what Black called 'fixed air' in 1754 Henry Cavendish discovered hydrogen and elucidated its properties and Joseph Priestley and, independently, Carl Wilhelm Scheele isolated pure oxygen.

English scientist John Dalton proposed the modern theory of atoms that all substances are composed of indivisible 'atoms' of matter and that different atoms have varying atomic weights.

The development of the electrochemical theory of chemical combinations occurred in the early 19th century as the result of the work of two scientists in particular, Jöns Jacob Berzelius and Humphry Davy, made possible by the prior invention of the voltaic pile by Alessandro Volta. Davy discovered nine new elements including the alkali metals by extracting them from their oxides with electric current. [61]

British William Prout first proposed ordering all the elements by their atomic weight as all atoms had a weight that was an exact multiple of the atomic weight of hydrogen. J.A.R. Newlands devised an early table of elements, which was then developed into the modern periodic table of elements [64] in the 1860s by Dmitri Mendeleev and independently by several other scientists including Julius Lothar Meyer. [65] [66] The inert gases, later called the noble gases were discovered by William Ramsay in collaboration with Lord Rayleigh at the end of the century, thereby filling in the basic structure of the table.

At the turn of the twentieth century the theoretical underpinnings of chemistry were finally understood due to a series of remarkable discoveries that succeeded in probing and discovering the very nature of the internal structure of atoms. In 1897, J.J. Thomson of Cambridge University discovered the electron and soon after the French scientist Becquerel as well as the couple Pierre and Marie Curie investigated the phenomenon of radioactivity. In a series of pioneering scattering experiments Ernest Rutherford at the University of Manchester discovered the internal structure of the atom and the existence of the proton, classified and explained the different types of radioactivity and successfully transmuted the first element by bombarding nitrogen with alpha particles.

His work on atomic structure was improved on by his students, the Danish physicist Niels Bohr and Henry Moseley. The electronic theory of chemical bonds and molecular orbitals was developed by the American scientists Linus Pauling and Gilbert N. Lewis.

The year 2011 was declared by the United Nations as the International Year of Chemistry. [67] It was an initiative of the International Union of Pure and Applied Chemistry, and of the United Nations Educational, Scientific, and Cultural Organization and involves chemical societies, academics, and institutions worldwide and relied on individual initiatives to organize local and regional activities.

Organic chemistry was developed by Justus von Liebig and others, following Friedrich Wöhler's synthesis of urea which proved that living organisms were, in theory, reducible to chemistry. [68] Other crucial 19th century advances were an understanding of valence bonding (Edward Frankland in 1852) and the application of thermodynamics to chemistry (J. W. Gibbs and Svante Arrhenius in the 1870s).

Subdisciplines

Chemistry is typically divided into several major sub-disciplines. There are also several main cross-disciplinary and more specialized fields of chemistry. [69]

    is the analysis of material samples to gain an understanding of their chemical composition and structure. Analytical chemistry incorporates standardized experimental methods in chemistry. These methods may be used in all subdisciplines of chemistry, excluding purely theoretical chemistry. is the study of the chemicals, chemical reactions and chemical interactions that take place in living organisms. Biochemistry and organic chemistry are closely related, as in medicinal chemistry or neurochemistry. Biochemistry is also associated with molecular biology and genetics. is the study of the properties and reactions of inorganic compounds. The distinction between organic and inorganic disciplines is not absolute and there is much overlap, most importantly in the sub-discipline of organometallic chemistry. is the preparation, characterization, and understanding of substances with a useful function. The field is a new breadth of study in graduate programs, and it integrates elements from all classical areas of chemistry with a focus on fundamental issues that are unique to materials. Primary systems of study include the chemistry of condensed phases (solids, liquids, polymers) and interfaces between different phases. is the study of neurochemicals including transmitters, peptides, proteins, lipids, sugars, and nucleic acids their interactions, and the roles they play in forming, maintaining, and modifying the nervous system. is the study of how subatomic particles come together and make nuclei. Modern Transmutation is a large component of nuclear chemistry, and the table of nuclides is an important result and tool for this field. is the study of the structure, properties, composition, mechanisms, and reactions of organic compounds. An organic compound is defined as any compound based on a carbon skeleton. is the study of the physical and fundamental basis of chemical systems and processes. In particular, the energetics and dynamics of such systems and processes are of interest to physical chemists. Important areas of study include chemical thermodynamics, chemical kinetics, electrochemistry, statistical mechanics, spectroscopy, and more recently, astrochemistry. [70] Physical chemistry has large overlap with molecular physics. Physical chemistry involves the use of infinitesimal calculus in deriving equations. It is usually associated with quantum chemistry and theoretical chemistry. Physical chemistry is a distinct discipline from chemical physics, but again, there is very strong overlap. is the study of chemistry via fundamental theoretical reasoning (usually within mathematics or physics). In particular the application of quantum mechanics to chemistry is called quantum chemistry. Since the end of the Second World War, the development of computers has allowed a systematic development of computational chemistry, which is the art of developing and applying computer programs for solving chemical problems. Theoretical chemistry has large overlap with (theoretical and experimental) condensed matter physics and molecular physics.

Other disciplines within chemistry are traditionally grouped by the type of matter being studied or the kind of study. These include inorganic chemistry, the study of inorganic matter organic chemistry, the study of organic (carbon-based) matter biochemistry, the study of substances found in biological organisms physical chemistry, the study of chemical processes using physical concepts such as thermodynamics and quantum mechanics and analytical chemistry, the analysis of material samples to gain an understanding of their chemical composition and structure. Many more specialized disciplines have emerged in recent years, e.g. neurochemistry the chemical study of the nervous system (see subdisciplines).

Industry

The chemical industry represents an important economic activity worldwide. The global top 50 chemical producers in 2013 had sales of US$980.5 billion with a profit margin of 10.3%. [71]


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2.1J: Hydrogen Bonding and Van der Waals Forces

  • Van der Waals interactions: A weak force of attraction between electrically neutral molecules that collide with or pass very close to each other
  • The van der Waals force is caused by temporary attractions between electron-rich regions of one …

Van der Waals forces in biological systems

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Van der Waals forces in biological systems 343 or submolecular groups depends on their mutual orientation.

Van der Waals forces and other non-covalent interactions

Diploes, Van der Waals Forces, and Pi Interactions There are several other types of non-covalent molecular interactions that we encounter in general biology: dipole-dipole interactions, Van der Waals forces and pi interactions (sometimes known as pi bonding).

Biology: Chemistry in Biology: 07: Van der Waals Forces

  • A hydrogen bond is a strong Van der Waals force between a polar molecule containing hydrogen atoms and the negative pole of another polar molecule
  • Van der Waals forces account for cohesion, the attraction between like molecules within a substance, and adhesion, the attraction between unlike molecules in different substances

Learn About Van Der Waals Forces In Dna Structure Chegg.com

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  • Van der Waal forces like ionic bonds, hydrogen bonds, and hydrophobic bonds are non-covalent bonds
  • They cause attraction and repulsion between molecules and surfaces and act by causing a change in the polarization of the nearby particles.

Van der Waals Forces Chemistry for Non-Majors

Van der Waals forces are the weakest intermolecular force and consist of dipole-dipole forces and dispersion forces.

Van der Waals forces chemistry and physics Britannica

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Van der Waals forces, relatively weak electric forces that attract neutral molecules to one another in gases, in liquefied and solidified gases, and in almost all organic liquids and solids.

Weaker Bonds in Biology Biology for Non-Majors I

  • Like hydrogen bonds, van der Waals interactions are weak attractions or interactions between molecules
  • They are also called inter-molecular forces
  • They occur between polar, covalently bound atoms in different molecules.

Electrostatic and van der Waals Interactions

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  • Van der Waals interactions (see Figure 1) represent the attraction of the nuclei and electron clouds between different atoms
  • The nucleus is positively charged, while the electrons around it are negatively charged
  • When two atoms are brought close together, the nucleus of one atom attracts the electron cloud of the other, and vice versa.

Van Der Waals Forces Definition of Van Der Waals Forces

Medical Definition of van der Waals forces : the relatively weak attractive forces that are operative between neutral atoms and molecules and that arise because of the electric polarization induced in each of the particles by the presence of other particles

Van der Waals forces in biological systems Quarterly

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  • The theory of van der Waals forces has now developed to a stage where it constitutes a powerful tool in theoretical investigations of many biological systems
  • In this review we shall consider both the theoretical and conceptual aspects of these forces with the emphasis on the way they may be involved in various biological processes.

Modeling of the Van Der Waals Forces during the Adhesion

  • Multiplying the unretarded van der Waals interaction potentials by f (D, λ) yields the approximate retarded van der Waals interaction potential
  • When using a bacterium as the macroscopic body, there is only a small difference (up to 10–30J) between retarded and non-retarded vdW forces, and therefore will be ignored in this study.

(PDF) Van der waals force Definition What is Van der

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  • Van der waals force Explanation Weak forces that are responsible for bond formation only when the atoms are in close proximity, these forces are much weaker than the ionic bonds or covalent bonds
  • Van der wails forces do not result from charge and only from …

Solutions to 7.012 Problem Set 1

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  • Covalent bond, ionic bond, hydrogen bond, or van der Waals forces)
  • Position Amino Acid(s) Interaction A any amino acid with a hydrophobic side chain alanine isoleucine, leucine methionine, phenylalanine, trypyophan, valine van der Waals forces B any of the charged or uncharged polar amino acid serine, threonine, asparigine, glutamine,

Van der Waals Forces: A Handbook for Biologists, Chemists

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  • Van der Waals Forces: A Handbook for Biologists, Chemists, Engineers, and Physicists - Kindle edition by Parsegian, V
  • Download it once and read it on your Kindle device, PC, phones or tablets
  • Use features like bookmarks, note taking and highlighting while reading Van der Waals Forces: A Handbook for Biologists, Chemists, Engineers, and Physicists.

Van der Waals Forces: A Handbook for Biologists, Chemists

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  • The Parsegian textbook is ideal for either teaching a segment of 6 to 9 lectures or teaching an entire course on Van der Waals forces - I have done both
  • Moreover, there is also advanced material included that is important for applications that range from biomembrane physics to wetting phenomena.

Van Der Waals Forces: study guides and answers on Quizlet

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Dipole Dipole Forces Van Der Waals Forces Atoms And Molecules Non Polar Molecules Gas Liquid Solid TERMS IN THIS SET (40)

Vander waals forces and its significance

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  • Vander Waals force • It is the sum of the attractive or repulsive forces between molecules
  • • These were named after -: Johannes Diderik van der Waals 3
  • Its main characteristics are:- They are weaker than normal covalent ionic bonds

Teacher Notes: Chemical Bonds and Forces – PEP

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  • Covalent compounds exhibit van der Waals intermolecular forces that form bonds of various strengths with other covalent compounds
  • The three types of van der Waals forces include: 1) dispersion (weak), 2) dipole-dipole (medium), and 3) hydrogen (strong)
  • Ion-dipole bonds (ionic species to covalent molecules) are formed between ions and polar

Van der Waals and hygroscopic forces of adhesion generated

  • van der Waals forces encompass two mechanisms: London dispersion forces and hygroscopic adhesion
  • The former depends only on the presence of nuclei and electrons and can operate between any two molecules that are in sufficiently close proximity (Hobsa and Zahradnik,1988)
  • These weak interactions arise when an instantaneous dipole in one

Van-der-Waals force up close: Physicists take new look at

  • Van der Waals forces are fundamental for chemistry, biology and physics
  • However, they are among the weakest known chemical interactions, so they are notoriously hard to study.

Controlling friction by tuning van der Waals forces

June 29, 2017 — Van der Waals interactions between molecules are among the most important forces in biology, physics, and chemistry, as they …


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2.1J: Hydrogen Bonding and Van der Waals Forces

  • Van der Waals Interactions Like hydrogen bonds, van der Waals interactions are weak attractions or interactions between molecules
  • Van der Waals attractions can occur between any two or more molecules and are dependent on slight fluctuations of the electron densities, which are not always symmetrical around an atom.

Could you explain van der Waals' forces to me, and their

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  • Dispersion forces are another of van der Waals' three forces
  • They exist between nonpolar molecules
  • For example, chlorine gas is made up of two chlorine atoms
  • In this bond, the electrons are equally shared and are not dominant on one side of the molecule as is the case in HCl.

7. Van der Waals Potential Energy

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  • The pairwise potential energy, V (r) , between two non-bonded atoms can be expressed as a function of internuclear separation, r , as follows, Graphically, if reqm is the equilibrium internuclear separation , and e is the well depth at reqm, then: The exponential, repulsive

Van der Waals Forces Chemistry for Non-Majors

  • Dipole-dipole forces are similar in nature, but much weaker than ionic bonds
  • Dispersion forces are also considered a type of van der Waals force and are the weakest of all intermolecular forces
  • They are often called London forces after Fritz London (1900-1954), who first proposed their existence in 1930.

Electrostatic and van der Waals Interactions

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  • Electrostatic and van der Waals Interactions
  • For example, Mg 2+ ions associate with the negatively charged phosphates of nucleotides and nucleic acids
  • Within proteins, salt bridges can form between nearby charged residues, for example, between a positively charged amino group and a negatively charged carboxylate ion.

Explanation of liquefaction using the Van der Waals

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  • The Van der Waals equations can be used not only to describe the behavior of real substances in the gas phase, but also to explain the phase transition from the gaseous state to the liquid state at high pressures
  • To show this, the Van der Waals equation is first rearranged so that the pressure p can be represented as a function of the volume V m:

Teacher Notes: Chemical Bonds and Forces – PEP

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  • Ion-dipole bonds (ionic species to covalent molecules) are formed between ions and polar molecules
  • These compounds typically form medium to strong bonds
  • There are five kinds of intermolecular forces described below the bond strengths described range from strongest to weakest (the latter 3 are examples of van der Waals forces).

Is a hydrogen bond considered to be a van der Waals force

  • According to the IUPAC gold book a van der Waals force is:
  • The attractive or repulsive forces between molecular entities (or between groups within the same molecular entity) other than those due to bond formation or to the electrostatic interaction of ions or of ionic groups with one another or with neutral molecules.

2.1I: Covalent Bonds and Other Bonds and Interactions

  • Hydrogen bonds and Van Der Waals are responsible for the folding of proteins, the binding of ligands to proteins, and many other processes between molecules
  • Key Terms hydrogen bond : A weak bond in which a hydrogen atom in one molecule is attracted to an electronegative atom (usually nitrogen or oxygen) in the same or different molecule.

Van der Waals intermolecular forces Vs Hydrogen bonds. How

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  • The above is just one example how hydrogen bonds make water unique
  • Water has several anomalous properties like water shrinks on melting, liquid water has

Van Der Waals Forces – Definition and Equation

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  • A Van Der Waals example of dipole-dipole forces is visible in hydrogen chloride (HCl) as a positive end of an element attracts the negative end of the other
  • Hydrogen Bonds: It is a special type of dipole-induced dipole interaction within hydrogen atoms
  • They are comparatively much stronger bonds than dipole-dipole interactions and London forces.

Difference Between Van der Waals and Hydrogen Bonds

  • Van der Waals forces and hydrogen bonds are intermolecular attractions between molecules
  • Some intermolecular forces are stronger, and some are weak
  • These bonds determine the behavior of molecules
  • For an intermolecular attraction, there should be a charge separation
  • There are some symmetrical molecules like H 2, Cl 2

Have You Heard of Van der Waals Force

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Are you excited and interested in today's chemistry online classes? Have You Heard of Van der Waals Force? If not then in this video Divyasha Ma'am will teac

Van der Waals forces chemistry and physics Britannica

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  • Van der Waals forces may arise from three sources
  • First, the molecules of some materials, although electrically neutral, may be permanent electric dipoles.Because of fixed distortion in the distribution of electric charge in the very structure of some molecules, one side of a molecule is always somewhat positive and the opposite side somewhat negative.

Van der Waals bond Flashcards and Study Sets Quizlet

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  • Browse 86 sets of Van der Waals bond flashcards
  • Study sets Diagrams Classes Users
  • Van der Waals Forces and metallic bonding
  • Attractions between instantaneous dipol…

ROCO Chapter 2 : van der Waals radius

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  • Van der Waals radii can be used to study nonbonded (especially intermolecular) interactions
  • For example, one can compare an actual nonbonded distance with a predicted distance (the latter is obtained by summing van der Waals radii)
  • If there is a “prediction gap”, that is, if the actual distance is substantially shorter than the predicted

Difference Between Van der Waals and Hydrogen Bonds

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Hydrogen bonding always occurs between two permanent dipoles, and is much stronger that the Van der Waals forces, which on the other hand, are found between the combination of either two permanent dipoles, dipole- induced dipole or two induced dipoles – meaning that they can be present without the presence of a permanent dipole.

Competition of van der Waals and chemical forces on gold

  • Figure 1: Ways that van der Waals dispersion forces can modify chemical bonding
  • The top row shows examples of how dispersion forces make existing bonds stronger and more stable in unusual geometries, whilst the bottom row shows dispersion forces leading to alternate chemical structures.

Intermolecular Forces (van der Waals Forces) in Organic

  • Intermolecular Forces (van der Waals Forces) in Organic compounds
  • ** The forces that act between molecules are not as strong as those between ions, but they account for the fact that even completely nonpolar molecules can exist in liquid and solid states.These intermolecular forces, collectively called van der Waals forces, are all electrical

Intermolecular Forces Boundless Chemistry

Van der Waals forces: The sum of the attractive or repulsive forces between molecules (or between parts of the same molecule) other than those due to covalent bonds, or the electrostatic interaction of ions with one another, with neutral molecules, or with charged molecules.


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Van der Waals interaction (also known as London dispersion

  • Van der Waals (VDW) interactions are probably the most basic type of interactionimaginable. Any two molecules experience Van der Waals interactions
  • Evenmacroscopic surfaces experience VDW interactions, but more of this later.

Van der Waals interactions definition of van der Waals

  • van der Waals interactions: the weak bonds formed between electrically neutral molecules or parts of molecules when they lie close together
  • Such interactions are common in the secondary and tertiary structure of protein.

Electrostatic and van der Waals Interactions

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  • Van der Waals interactions (see Figure 1) represent the attraction of the nuclei and electron clouds between different atoms. The nucleus is positively charged, while the electrons around it are negatively charged
  • When two atoms are brought close together, the nucleus of one atom attracts the electron cloud of the other, and vice versa.

Lifshitz–van der Waals (LW) Interactions Taylor

  • der Waals forces (van Oss, Omenyi and Neumann, 1979 Neumann, Omenyi and van Oss, 1979)
  • It should be clear that these conditions are by no means rare or exceptional
  • Hamaker already indicated the possibility of such repulsive (dispersion) forces (1937a), which possibility was …

Van der Waals integration before and beyond two

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The vdW interaction 21, 22, named after Dutch scientist Johannes Diderik van der Waals, generally includes three different types of intermolecular interactions: dipole–dipole interaction …

2.1J: Hydrogen Bonding and Van der Waals Forces

Van der Waals Interactions Like hydrogen bonds, van der Waals interactions are weak attractions or interactions between molecules. Van der Waals attractions can occur between any two or more molecules and are dependent on slight fluctuations of the electron densities, which are not always symmetrical around an atom.

Van der Waals Forces Chemistry for Non-Majors

  • Van der Waals forces are weak interactions between molecules that involve dipoles. Polar molecules have permanent dipole-dipole interactions

The van der Waals interaction: American Journal of Physics

  • The interaction between two neutral but polarizable systems at separation R, usually called the van der Waals force, is discussed from different points of view
  • The change in character from 1/R 6 to 1/R 7 due to retardation is explained.

Van der Waals Interactions Measured for the First Time

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  • Van der Waals interactions are one of the weakest interactions known to our world
  • Nevertheless, they are very important and you can find them …

Interfacial Lifshitz-van der Waals and Polar Interactions

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  • Llfshltz-van der Waals (LW) Interactions In the Condensed State 1
  • Lifshitr Approach The Lifshitz theory of condensed media interaction41 has its origin in Maxwell’s equations, where the electric and magnetic fields are subjected to fast temporal fluctuations
  • In order to accommodate the temporal

Van der Waals Flashcards Quizlet

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  • How does a Van Der Waals interaction occur? If 2 atoms are close together, then when the e- on one atom happens to be on one side, then it is favorable for the neighboring ones to be on the other side, you form a weak pair of dipoles (like induction)

Lifshitz-Van Der Waals Interaction

Lifshitz-van der Waals (LW) interactions refer to the purely physical London's (dispersion), the Keesom's (polar) and Debye's (induced polar) interactions and correspond to magnitudes ranging from approximately 0.1 to 10 kJ/mol (but in rare cases may be higher).

Van der Waals forces and other non-covalent interactions

  • All molecules can experience Van der Waals forces, a type of molecular interaction found when molecules get very close together, typically at distances between 4-5 Angstroms
  • Just for reference, recall that 1 Angstrom = 10-10 meters
  • Van der Waals forces are, yet again, based on the attraction or repulsion of electrical poles.

Van der Waals interactions at the nanoscale: The effects

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  • The van der Waals interaction is a ubiquitous but subtle force between particles mediated by quantum fluctuations of charge
  • It is the most long-range force acting between particles and influences a range of phenomena such as surface adhesion, friction, and colloid stability.

Ionic and Covalent Bonds, Hydrogen Bonds, van der Waals

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  • There are four types of chemical bonds essential for life to exist: Ionic Bonds, Covalent Bonds, Hydrogen Bonds, and van der Waals interactions

Enhanced Chiral Discriminatory van der Waals Interactions

  • The van der Waals interaction is discriminatory with respect to enantiomers of different handedness and could be used to separate enantiomers
  • We also suggest a specific geometric configuration where the electric contribution to the van der Waals interaction is …

Van der Waals interactions (London dispersion forces

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Van der Waals interactions (London dispersion forces) are attractive forces that arise due to The hydrophobic effect Permanent dipoles of molecules containing covalent bonds between atoms of very different electronegativities lon pairing between oppositely charged functional groups Infinitesimal dipoles generated by the constant random motion

Van Der Waals Interactions: study guides and answers on

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  • Whether you have hours at your disposal, or just a few minutes, Van Der Waals Interactions study sets are an efficient way to maximize your learning time
  • Flip through key facts, definitions, synonyms, theories, and meanings in Van Der Waals Interactions when you’re waiting for an appointment or have a short break between classes.

Van der Waals intermolecular forces Vs Hydrogen bonds. How

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  • Water's hydrogen bonding holds water molecules up to about 15% closer than if water was a simple liquid with just Van der Waals dispersion interactions

Molecular ‘compass’ traces van der Waals interactions

A recently developed electron microscopy technique has allowed scientists to measure van der Waals interactions by precisely imaging the changes in orientation of individual para-xylene

Intermolecular Forces: Van der Waals Force, Hydrogen Bond

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  • Van der Waals force Hydrophobic interaction (Hydrophobic effect) Once you understand molecular polarization, you can understand why dipole interactions, hydrogen bonds, and van der Waals forces occur
  • Although hydrophobic interactions are a slightly different concept, it is essential when learning about molecular interactions

Van der Waals interaction affects wrinkle formation in two

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Two-dimensional crystals, arranged into van der Waals heterostructures, allow full control over the mechanical properties of the components and the interaction between them, making such experiments easy to reproduce and allowing one to understand the basic, underlying physics of …

Van Der Waals Forces – Definition and Equation

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  • Van Der Waals dispersion forces are close-knit interactions depending on distance resulting in intermolecular attractions or repulsions
  • These bonds get stronger when they lie in a range of 0.4 kilojoules per mole (kJ/mol) and 4 kJ/mol.

Graphene fatigue through van der Waals interactions

  • Van der Waals (vdW) interactions are among the weakest intermolecular forces, which are generally much weaker than intramolecular forces, such as covalent bonding (3)

How Geckos Stick on der Waals Science AAAS

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  • Scientists have put to rest the age-old question of how geckos stick to walls
  • The answer is van der Waals forces, molecular attractions that …

Using a new kind of electron microscopy to measure weak

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Van der Waals forces are electrostatic forces between uncharged molecules—they arise due to the interaction between electric dipole moments—measuring them typically …

Van der Waals interaction between internal aqueous

  • The overall van der Waals interaction across the oil film is a combined result of four individual parts, that is, W(1)-W(2), A(1)-A(2), W(1)-A(1), and A(2)-W(2) van der Waals interaction, and it may be either attractive or repulsive depending on many factors
  • It was found that the overall van der Waals interaction is dominated by the W(1)-W(2

Van der Waals interactions and the limits of isolated atom

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Van der Waals forces are among the weakest, yet most decisive interactions governing condensation and aggregation processes and the phase behaviour of …


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Definition of van der Waals interactions in Biology.

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  • The van der Waals model offers a reasonable approximation for real gases at moderately high pressures
  • Distinguish the van der Waals equation from the Ideal Gas Law
  • London dispersion forces are part of the van der Waals forces, or weak intermolecular attractions
  • Van der Waals forces help explain how nitrogen can be liquefied.

2.1J: Hydrogen Bonding and Van der Waals Forces

  • van der Waals interactions: A weak force of attraction between electrically neutral molecules that collide with or pass very close to each other.The van der Waals force is caused by temporary attractions between electron-rich regions of one …

Van der Waals forces and other non-covalent interactions

  • All molecules can experience Van der Waals forces, a type of molecular interaction found when molecules get very close together, typically at distances between 4-5 Angstroms
  • Just for reference, recall that 1 Angstrom = 10-10 meters
  • Van der Waals forces are, yet again, based on the attraction or repulsion of electrical poles.

Van der Waals interaction (also known as London dispersion

  • Van der Waals (VDW) interactions are probably the most basic type of interaction imaginable
  • Any two molecules experience Van der Waals interactions
  • Even macroscopic surfaces experience VDW interactions, but more of this later
  • The physical process that leads to Van der Waals interactions is clear, but it is difficult to

Many-Body van der Waals Interactions in Biology, Chemistry

  • 1 SCIENTIFIC HIGHLIGHT OF THE MONTH Many-Body van der Waals Interactions in Biology, Chemistry, and Physics Robert A
  • Gobre2, and Alexandre Tkatchenko2 1Department of Chemistry, Princeton University, Princeton, NJ 08544, USA 2Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195, Berlin, Germany [email protected], …

Electrostatic and van der Waals Interactions

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  • Van der Waals interactions (see Figure 1) represent the attraction of the nuclei and electron clouds between different atoms.The nucleus is positively charged, while the electrons around it are negatively charged
  • When two atoms are brought close together, the nucleus of one atom attracts the electron cloud of the other, and vice versa.

First-Principles Models for van der Waals Interactions in

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  • Noncovalent van der Waals (vdW) or dispersion forces are ubiquitous in nature and influence the structure, stability, dynamics, and function of molecules and materials throughout chemistry, biology, physics, and materials science
  • These forces are quantum mechanical in origin and arise from electrostatic interactions between fluctuations in the electronic charge density.

Van der Waals Forces Chemistry for Non-Majors

  • Van der Waals forces are weak interactions between molecules that involve dipoles
  • Polar molecules have permanent dipole-dipole interactions
  • Non-polar molecules can interact by way of London dispersion forces
  • Use the link below to answer the following questions:

Weaker Bonds in Biology Biology for Non-Majors I

  • Like hydrogen bonds, van der Waals interactions are weak attractions or interactions between molecules
  • They are also called inter-molecular forces
  • They occur between polar, covalently bound atoms in different molecules.

Imaging van der Waals Interactions The Journal of

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  • The van der Waals interactions are responsible for a large diversity of structures and functions in chemistry, biology, and materials
  • Discussion of van der Waals interactions has focused on the attractive potential energy that varies as the inverse power of the distance between the two interacting partners
  • The origin of the attractive force is widely discussed as being due to the correlated

Van der Waals forces in biological systems

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  • Van der Waals force isn biological systems JACOB N
  • ISRAELACHVIL I Stockholm University, Biophysics Institute, Arrhenius Laboratory, Fack, 5-104 Stockholm, 05 Sweden INTRODUCTION 342 I
  • VAN DER WAALS INTERACTIONS BETWEEN ATOMS, MOLECULES, AN SMALD L PARTICLE 34S 4 1.1
  • The van der Waals interaction between two small particles in free space 344 1.2.

Ionic and Covalent Bonds, Hydrogen Bonds, van der Waals

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  • There are four types of chemical bonds essential for life to exist: Ionic Bonds, Covalent Bonds, Hydrogen Bonds, and van der Waals interactions

Role of van der Waals Interactions in Physics, Chemistry

  • (Long-Range) Van der Waals Interactions Failure of DFT Approximations for (Long-Range) Van der Waals Interactions EX+cRPA is O.K., though the C 6 coefficient is slightly too small
  • In general, using “standard xc functionals”: o Intermolecular equilibrium distances are over-estimated by as much as an Angstrom or more

The van der Waals interaction between protein molecules in

  • Formulation to estimate such interactions
  • It should be noted that our formulation is distinctly different from the van der Waals interactions in force field models used in molecular simulations
  • In that case the van der Waals interaction pa-rameters are obtained from …

Scaling laws for van der Waals interactions in

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  • Van der Waals interactions have a fundamental role in biology, physics and chemistry, in particular in the self-assembly and the ensuing function of nanostructured materials
  • Here we utilize an efficient microscopic method to demonstrate that van der Waals interactions in

Van der Waals Interactions Protocol

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  • Van der Waals interactions are so strong cumulatively that they can hold the weight of a gecko! This amazing feat is managed through the many interactions between the molecules on the tips of hairs on the gecko and molecules on the wall's surface.

Van der Waals interactions definition of van der Waals

  • van der Waals interactions: the weak bonds formed between electrically neutral molecules or parts of molecules when they lie close together
  • Such interactions are common in the secondary and tertiary structure of protein.

Materials perspective on Casimir and van der Waals

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  • Ab Initio Methods for van der Waals Forces 3 A
  • Exact nonrelativistic treatment of microscopic van der Waals interactions 4 B
  • Response functions and polarization waves 4 C
  • Approximate microscopic methods for van der Waals interactions 5 1
  • Two-point density functionals for van der Waals interactions 6 2
  • Fragment-based methods for van der

Van der Waals Flashcards Quizlet

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    The desire to be at its lowest possible energy, distance where this happens is

Fundamentals of van der Waals and Casimir Interactions

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This book presents the basics of van der Waals and Casimir interactions, displays van der Waals and Casimir interactions in microscopic, mesoscopic, and macroscopic systems, and summarizes applications of van der Waals and Casimir interactions in physics, chemistry, biology

Learn About Van Der Waals Forces In Dna Structure Chegg.com

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  • Van der Waals forces are of different types- Keesom interactions, Debye forces, and London Dispersion forces
  • Two factors that affect the Van der Waal forces are the number of electrons held by the atoms and the shape of the molecule
  • Van der Waals force plays a fundamental role in various fields and is also known to stabilize the DNA double helix.

Van Der Waals Interactions: study guides and answers on

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  • Van Der Waals Interactions Three Dimensional Shapes Naturally Occurring Elements Making And Breaking High Specific Heat
  • TERMS IN THIS SET (49) In the term trace element, the adjective trace means that
  • The element is required in very small amounts

Nonadditivity in van der Waals interactions within multilayers

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  • Nonadditivity in van der Waals interactions within multilayers R
  • Podgornika Laboratory of Physical and Structural Biology, NICHD, Building 9 Room 1E116, National Institutes of Health, Bethesda, Maryland 20892-0924 Faculty of Mathematics and Physics, University of Ljubljana,

How are these ordered from strongest to weakest: hydrogen

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  • Biology Chemistry Earth Science #"4
  • van der Waals interactions.."# Explanation: This is the conventional order
  • Ionic bonds are of course non-molecular interactions

Controlling friction by tuning van der Waals forces

June 29, 2017 — Van der Waals interactions between molecules are among the most important forces in biology, physics, and chemistry, as they …

Van der Waals forces in biological systems Quarterly

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  • The theory of van der Waals forces has now developed to a stage where it constitutes a powerful tool in theoretical investigations of many biological systems
  • In this review we shall consider both the theoretical and conceptual aspects of these forces with the emphasis on the way they may be involved in various biological processes.

Van der Waals interactions in a dielectric with

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  • van der Waals interactions thrives,2 its results essential in condensed matter physics, high-energy physics, colloid sci-ence, and cosmology.3 The approximations on which it is based are usually realistic and lead to results that can be reliably compared with measurement
  • One restrictive condi-tion built into the theory is the assumed steplike

Tailoring van der Waals dispersion interactions with

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van der Waals (vdW) dispersion interactions play an important role in the structure formation, energetic stability, and reaction mechanisms for a …