Which of the following Group `15` elements do not show allotropy?

Options

A. `N` and`As`
B. `N` and `Sb`
C. `N` and `Bi`
D. `As` and `Sb`

Answer

3

Explanation

Except `N` and `Bi` , all the group `15` elements exhibits allotropy.
The allotroph of phosphorous is rather complex but essentially , there are three allotropic forms known as white, red and black phosphorous . Arsenic and antimony also exhibit allotrophy , an unstable form of each element ,structurally similar to that of white phosphorus being formed by rapid condensation of their capours. this unstable form is readily transformed into a denser allotrope which is metallic and similar in structure to that of black phosphorus. Bismuth does not exhibit allotroph and adopts this latter structure(i.e. the layer structure).
Bismuth is unusual, because the expands when it forms the silid. This unsual behaviour is also found with `Ga` and `Ge` .