Group 15 elements allotropy

All five of the Group VI elements have a property called allotropy, which means they exist in more than one solid form. Like carbon, which could be black graphite or a sparkling diamond, these elements can exist with their atoms arranged in more than one way. 

Give a brief account of allotropy among the group 15 elements. 

Primary allotropy is well known in only nine elements C, O, P, S, As, Se, Sn, Sb, and Te. Table 21.2 shows how they are grouped near the zig-zag line that serves roughly as a borderline between the metallic and the nonmetallic elements (see also Table 7.4, page 109). 

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