The Group 15 Elements P, As, Sb, Bi

The electronic structures and some other properties of the elements in Group 15 are listed in Table 10-1. The valence shells have a structure formally similar to that of nitrogen, but beyond the stoichiometries of some of the simpler compounds— NH3, PH3, NC13, BiCl3, for example—there is little resemblance between the characteristics of compounds of these elements and those of nitrogen. 

The only naturally occurring isotope of phosphorus (31P) has a nuclear spin of V2 and a large magnetic moment. Nuclear magnetic resonance spectroscopy has accordingly played an extremely important role in the study of phosphorus compounds.1 For antimony, the isotope 121Sb is suitable for Mossbauer spectroscopy. 

Some of the more important trends are shown by the oxides, which change from acidic for phosphorus to basic for bismuth, and by the halides, which have increasingly ionic character PC13 is instantly hydrolyzed by water to HPO(OH)2, and the other trihalides give initially clear solutions that hydrolyze to As203, SbOCl, and BiOCl, respectively. There is also an increase in the stability of the lower 

Electronic structure [Ne]3r23p3 [Ar]3 f °4s24p3 [Kr]4 f °5s25p3 [Xe]4/145 f106i26p3 

Oxidation states or oxidation numbers of III (+3) or V (+5) can be, and often are, assigned to these elements in their compounds and are useful for purposes of classification. However, they are purely formal. What matters is the number of covalent bonds formed and the stereochemistries. The general types of compound and stereochemical possibilities are given in Table 10-2. 

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