Electron affinity outermost electrons

Atoms like Na, K and Mg demonstrate a low affinity for electrons. The loss of one or two electrons depletes their outer electron shell resulting in their next lower (completely full) electron shell being their outermost shell. 

Fig. 7.1 Schematic diagram of total electronic energy as a function of fractional occupation number variation, An. Ionization potential (IP) and electron affinity (EA) are defined as E(An = —1) — E(An = 0) and E(An = 0) — E(An = +1), respectively. Based on the Janak theorem, the gradient of the total energy is HOMO energy for An = —0 and LUMO energy for An = +0. The fineariy varied total energies also indicate that the outermost orbital energies are kept constant for the fractional occupation...

In this equation, IP and EA are the ionization potential and electron affinity, respectively, and em( ) is the w-th orbital energy of the system containing n electrons. Sham and Schliiter (1985) established that this energy error corresponds to the orbital energy variation for increasing numbers of electrons in the outermost orbitals. 

The screening effect is the effect the electrons in the lower energy levels (nearer the interior of the atom) have on those in the outermost levels. They, in effect, screen the outermost electrons from the pull of the nucleus because they are like-charged. This results in lower ionization energy, lower electron affinity, and larger atoms near the bottom within a family. 

The electron affinity is the energy gained when an electron is added to a neutral gas-phase atom, and so Mulliken s electronegativities average the ability of a neutral atom to retain its outermost electrons and its ability to attract an additional electron to form an anion. 

The terms oxidation and reduction with respect to chemical processes in soil-water systems refers to potential electron-transfer processes. Under oxidation, a chemical element or molecular species donates electrons (e ), whereas under reduction a chemical element or molecular species accepts electrons. The potential of an atom of any given element to react depends on the affinity of its nucleus for electrons and the strong tendency of the atom to gain maximum stability by filling its outer electron shell or comply with the octet rule. The octet rule states that to gain maximum stability an atom must have eight electrons in its outer shell or outermost energy level. 

Langmuir s conception of the structure of the atom also threw a flood of light upon the meaning of isotopes—atoms of the same chemical and physical properties but differing in mass. Since chemical affinity depends upon the electrons in the outermost shell, Langmuir believed chlorine isotopes, for example, to have the same number of electrons outside the nucleus. Each chlorine isotope has seventeen free electrons of which seven are in the outermost shell. Since, however, they... 

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