Ions, isolated, electron affinity

The electron affinity of an element is defined as the amount of energy absorbed when an electron is added to an isolated gaseous atom to form an ion with a 1- charge. 

The noble gas hydride ions should have a bond order of one and tbe diatomic noble gas ions should have a bond order of one-half. Neither type cun be isolated in the form of salts of the type HeH+X or He, X- since the electron affinity of positive helium, etc. is greater than that of any appropriate species X, and so such salts would spontaneously decompose ... 

Cesium has the smallest ionization energy of all elements (376 kj/mol), and chlorine has the most negative electron affinity (—349 kj/mol). Will a cesium atom donate an electron to a chlorine atom to form isolated Cs+ and Cl- ions ... 

The electron affinity values for atoms among the first 20 elements that form stable, isolated X ions. The lines shown connect adjacent elements. The absence of a line indicates missing elements (He, Be, N, Ne, Mg, and Ar) whose atoms do not add an electron exothermically and thus do not form stable, isolated X- ions. 

Electron affinity The amount of energy absorbed in the process in which an electron is added to a neutral isolated gaseous atom to form a gaseous ion with a 1 — charge has a negative value if energy is released. 

In isolation such a tetrahedron has a strong electron affinity. Since the bond to the silicon atom employs only one of the bonding electrons of an oxygen atom, there is room in each for one more electron in an atomic orbital of principal quantum number 2. Hence an isolated Si04 group readily forms the negative orthosilicate ion, Si04 (Fig. 9.8). 

The azide ion has not been observed in nature as an isolated species. It is, however, readily stabilized by a lattice or solution environment. Many of the ion s properties tend to be similar to those of halogen ions when it is ionically bonded or in solution. Indeed, X-ray structural data on NaNa and KN3 reveal that the ion is a compact prolate spheroid (see Chapter 3) comparable in volume to Br its electron affinity (see below) is also close to that of Br . 

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