Electron affinity variation

C08-0032. Describe periodic variations in electron configurations explain how they affect ionization energy and electron affinity. 

However, for other reactions an opposite trend is observed. There are undoubtedly several factors involved, which include F forming the strongest bridge but I being the best "conductor" for the electron being transferred because it is much easier to distort the electron cloud of I- (it is much more polarizable and has a lower electron affinity). Therefore, in different reactions these effects may take on different weights, leading to variations in the rates of electron transfer that do not follow a particular order with respect the identity of the anion. 

Nonmetals follow the general trends of atomic radii, ionization energy, and electron affinity. Radii increase to the left in any row and down any column on the periodic table. Ionization energies and electron affinities increase up any column and towards the right in any row on the periodic table. The noble gases do not have electron affinity values. Ionization energies are not very important for the nonmetals because they normally form anions. Variations appear whenever the nonmetal has a half-filled or filled subshell of electrons. The electronegativity... 

This section summarizes the variation, across the periods and down the groups of the Periodic Table, of (i) the ionization energies, (ii) the electron attachment energies (electron affinities), (iii) the atomic sizes and (iv) the electronegativity coefficients of the elements. 

In die Pople family of basis sets, the presence of diffuse functions is indicated by a + in die basis set name. Thus, 6-31- -G(d) indicates that heavy atoms have been augmented with an additional one s and one set of p functions having small exponents. A second plus indicates the presence of diffuse s functions on H, e.g., 6-311- -- -G(3df,2pd). For the Pople basis sets, die exponents for the diffuse functions were variationally optimized on the anionic one-heavy-atom hydrides, e.g., BH2 , and are die same for 3-21G, 6-3IG, and 6-3IIG. In the general case, a rough rule of thumb is diat diffuse functions should have an exponent about a factor of four smaller than the smallest valence exponent. Diffuse sp sets have also been defined for use in conjunction widi die MIDI and MIDIY basis sets, generating MIDIX+ and MIDIY-I-, respectively (Lynch and Truhlar 2004) the former basis set appears pardcularly efficient for the computation of accurate electron affinities. 

Figure 1.47 shows the variation in electron affinity in the main groups of the periodic table. It is much less periodic than the variation in... 

Methyl substitution decreases the gas-phase acidity of the Ge system similarly to what has been found in methylsilane191. On the other hand, the increase observed in trimethyl-germane is more difficult to analyze as relative variations of A//°cjd along a given family reflect changes in electron affinity and in Ge—H bond dissociation energies. 

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