Atomic electron affinities

Since electronegativity is the measure of an element s affinity for electrons (how willing the atom will be to accept a new electron), we can say that a negative charge on oxygen will be more stable than a negative charge on carbon. 

Energy is released when an electron is added to a fluorine atom to form a fluoride anion. In other words, a fluoride anion is more stable than a fluorine atom plus a free electron. Another way of saying this is that fluorine atoms have an affinity for electrons. 

Return to the case of LiF. Lithium ionizes readily, but has little affinity for electrons (I = ionization energy = 5.4 eV and A = electron affinity = 0eV.). On the other hand, fluorine is difficult to ionize, but has considerable electron affinity (I = 17.4eV. and A = -3.6eV.). Thus, when Li and F atoms are close neighbors, electrons can transfer to make Li+ and I. These then attract electrostatically until compression of their ion-cores prevent them from contracting further. In a solid crystal, there are both attractive +/- pairs, and repulsive (+/+ as well as -/-) pairs. However, for large arrays, there is a net attraction. This can be shown most simply by examining a linear chain of +q, and -q charges (Kittel, 1966). 

Electron affinity is the energy change that occurs when an electron is added to a gaseous atom (or ion). Since the electron affinity process usually is exothermic for atoms, most atomic electron affinities are negative. 

At this point, we have reached the stage where we can describe the adatom-substrate system in terms of the ANG Hamiltonian (Muscat and Newns 1978, Grimley 1983). We consider the case of anionic chemisorption ( 1.2.2), where a j-spin electron in the substrate level e, below the Fermi level (FL) eF, hops over into the affinity level (A) of the adatom, whose j-spin electron resides in the lower ionization level (I), as in Fig. 4.1. Thus, the intra-atomic electron Coulomb repulsion energy on the adatom (a) is... 

Atoms of elements in group 1 (lA) and group 2 (IIA) have low ionization energies and low electron affinities. Atoms of these elements give up electrons easily, hut attract them poorly. Therefore, they form positive ions in ionic compounds. 

Symbol B atomic number 5 atomic weight 10.811 a Group III A (Group 13) metalloid element atomic volume 4.70 cc/g-atom electron affinity 0.277 eV electronic configuration Is22s22pi valence state +3 naturally occurring stable isotopes are B-10 and B-11 and their abundance 19.57% and 80.43%, respectively. 

Electron Affinity (EA). Electron affinity is the reverse process to the ionization energy it is the energy change (often expressed in eV) associated with an isolated gaseous atom accepting one electron ... 

Note that Table 2.6 lists several molecules that have much higher electron affinities than fluorine (328.0 kJ mol" ) or chlorine (349.0 kJ mol" ). For example, consider PtF6 (772 kJ mol ). How can a molecule composed of six fluorine atoms and a metal (to be sure, not a very electropositive one) have a higher affinity for electrons than a fluorine atom ... 

Halogen, X Atomic ionization potential (eV) Atomic electron affinity (eV) Atomic radius (A) Atomic polarizabilityc (A3) Bond length of x2 molecule, i e(A) Dissociation energy of X2 molecule, Dc (kcal mol-1)... 

The effect of these atomic layers of foreign atoms adhering to the surface is undoubtedly due to an alteration in the strength of the double layer at the surface of the metal. If positive ions of a metal identical with the underlying metal are deposited on its surface, and the deficiency in electrons made up by supply through a wire, which is essentially what occurs in electrodeposition of a metal on the same metal, the free electrons flow out to the new surface layers, and the strength of the double layer at the surface is not altered by the new surface layer. But if the metal deposited on the surface has a smaller affinity for electrons than the... 

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