Electrical attraction

The word is also used to denote a unit in a solid crystal of an electrovalent compound such as NaCl in which each Na is electrically attracted by the surrounding six Cl" and each Cl" is electrically attracted by the surrounding six Na. The structure of such crystals is termed ionic to indicate that the crystal is not an aggregate of independent molecules. 

Physisorption occurs when, as a result of energy differences and/or electrical attractive forces (weak van der Waals forces), the adsorbate molecules become physically fastened to the adsorbent molecules. This type of adsorption is multilayered that is, each molecular layer forms on top of the previous layer with the number of layers being proportional to the contaminant concentration. More molecular layers form with higher concentrations of contaminant in solution. When a chemical compound is produced by the reaction between the adsorbed molecule and the adsorbent, chemisorption occurs. Unlike physisorption, this process is one molecule thick and irreversible... 

Polar reactions occur because of the electrical attraction between positive and negative centers on functional groups in molecules. To see how these reactions take place, let s first recall the discussion of polar covalent bonds in Section 2.1 and then look more deeply into the effects of bond polarity on organic molecules. 

Dispersion force. Temporary dipoles in adjacent molecules line up to create an electrical attraction force known as the dispersion force. Deeply shaded areas indicate regions where the electron cloud is momentarily concentrated and creates partial charges, indicated by (+) and (-). 

Polar molecules, like nonpolar molecules, are attracted to one another by dispersion forces. In addition, they experience dipole forces as illustrated in Figure 9.9, which shows the orientation of polar molecules, such as Id, in a crystal. Adjacent molecules line up so that the negative pole of one molecule (small Q atom) is as dose as possible to the positive pole (large I atom) of its neighbor. Under these conditions, there is an electrical attractive force, referred to as a dipole force, between adjacent polar molecules. 

It is possible to remove two or more electrons from a many-electron atom. Of course it is always harder to remove the second electron than the first because the second electron to come off leaves an ion with a double positive charge instead of a single positive charge. This gives an additional electrical attraction. Even so, the values of successive ionization energies have great interest to the chemist. 

When an atom absorbs a photon, the gain in energy promotes an electron to a less stable orbital. As electrons move into less stable orbitals, they have less electrical attraction for the nucleus. If the absorbed photon has enough energy, an electron can be ejected from the atom, as occurs in photoelectron spectroscopy. 

The ionic model describes a number of metal halides, oxides, and sulfides, but it does not describe most other chemical substances adequately. Whereas substances such as CaO, NaCl, and M 2 behave like simple cations and anions held together by electrical attraction, substances such as CO, CI2, and HE do not. In a crystal of Mgp2, electrons have been transferred from magnesium atoms to fluorine atoms, but the stability of HE molecules arises from the sharing of electrons between hydrogen atoms and fluorine atoms. We describe electron sharing, which is central to molecular stability, in Chapters 9 and 10. 

The chemicai bond in F2 forms from strong electrical attraction of the electron in the fluorine 2 p orbital ... 

Bond polarity also contributes to bond length because partial charges generate electrical attraction that pulls the atoms closer together. For example, notice in Table 9 that C—O bonds are slightly shorter than either C—C or O—O bonds. This is a result of the polarity of the C—O bond. 

Polar bonds gain stability from the electrical attraction between the negative and positive fractional charges around the bonded atoms. Bonds between oxygen and other second-row elements exemplily this trend ... 

As the charge on the metal ion increases, electrical attraction pulls the ligands closer to the cation. This leads to greater repulsive interactions between valence d electrons and ligand electrons. 

Air bubbles adhering to the insoluble solids by electrical attraction... 

Based on these contributions (a-d), we may arrive at the predictive scheme presented in Table 1. Because of the relatively large contribution from dehydration, essentially all proteins adsorb from an aqueous environment on apolar surfaces, even under electrostatically adverse conditions. With respect to polar surfaces, distinction may be made between proteins having a strong internal coherence ( hard proteins) and those having a weak internal coherence ( soft proteins). The hard proteins adsorb at polar surfaces only if they are electrically attracted, whereas the structural rearrangements (i.e., reductions in ordered structure) in the soft proteins lead to a sufficiently large increase in conformational entropy to make them adsorb at a polar, electrostatically repelling surface. 

When electrical attraction and repulsion operate over distances considerably larger than the hydrated sizes of the ions, we can compute species activities quite well from electrostatic theory, as demonstrated in the 1920s by the celebrated physical chemists Debye and Hiickel. At moderate concentrations, however, the ions pack together rather tightly. In a one molal solution, for example, just a few... 

Note that the long-range classical electrostatic limit furnishes an excellent approximation for the electrical attraction of the end groups, since these are separated far outside the range of significant exchange interactions. 

Fe3+. There are several ways of defining electronegativity, the simplest being that of Allred and Rochow (1958), which calculates the force experienced by the outer electron from the nucleus using Coulomb s law of electrical attraction ... 

Exchange Characterized by electrical attraction between the sorbate and the surface exemplified by ion-exchange processes. 

The term "affinity" has its roots in very old ideas to the effect that like attracts like and that bodies combine with other bodies because of mutual affection or affinitas. This meaning is employed in Etienne Francois Geoffroy s Table des differents rapports observes entre differentes substances (1718) for replacement reactions.28 However, in the middle of the eighteenth century, Boerhaave spoke of the affinity of a substance for others unlike it, giving the word "affinity" a new meaning. Boerhaave interpreted Geoffroy s table as a representation of Newtonian-type forces of gravitational attraction or electrical attraction and repulsion.29... 

Although this simile is now known to miss the mark, its historical importance cannot be denied. The centrifugal force victoriously opposes the electrical attraction and conversely, for each electron. A wonderful merry-go-round (dynamical equilibrium) is the result. In this idyllic version, the revolving motion of the electrons would go on forever, if the atom were not subjected to external infiuences, namely, collisions with other atoms, electrons and photons. Deformed to varying degrees by these impacts, atoms always tend to restore themselves in the most harmonious way, evacuating the excess energy acquired from the collision. 

Shortly after coming to Rutherford s laboratory, Bohr set to work on the problem of understanding the structure of atoms. Rutherford s discovery of the atomic nucleus had introduced formidable problems. It seemed necessary to assume that the electrons in an atom orbited the nucleus. Otherwise, the electrical attraction between the electrons and the nucleus would cause the electrons and the nucleus to collide with one another. But, as we have seen, the assumption that the electrons orbited the nucleus didn t seem to work either. Orbiting electrons should lose energy and fall into the nucleus anyway. 

Particles such as electrons and muons are not made up of quarks, and they are thus insensitive to the strong force. It is electrical attraction between unlike charges that binds electrons in atoms. Both electrons and muons belong to a class of particles called leptons, and there are six of them, just as there are six quarks. The six leptons are the electron, the muon, the tauon (named after the Greek letter tau), and three different kinds of neutrinos, which are called electron neutrino, muon neutrino, and tauon neutrino. 

The four forces are gravity, electromagnetism (electrical attraction and repulsion and magnetic forces are explained by the same theory), and the strong and weak nuclear forces. The weak force is... 

The assumption of the idea of completely rigid, spherical ions. In fact, the distance between the ions is markedly influenced by the magnitude of the electric attraction between the ions, so that the F ion behaves as a smaller ion when linked to a hexavalent S6+ ion, than when it is bound to a Na+ ion (see Section 71). 

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