Question

Which of the following statements regarding the allotropes of Nitrogen are correct? Assume the pressure to be atmospheric pressure at all times

• A. Below $-{237.6}^{\circ }C$ Nitrogen exists as the $\alpha$-nitrogen
• B. Gaseous nitrogen condenses into the $\beta$-nitrogen form at $-{210.01}^{\circ }C$
• C. As a gaseous diatomic molecule, Nitrogen does not have any allotropes at room temperature
• D. Nitrogen does not have any other allotropes under any circumstances

Answer 1

Answer: (A), (B), (C)

As a gaseous diatomic molecule, Nitrogen does not have any allotropes at room temperature

Nitrogen atom is small in size and has the tendency to form $p\pi -p\pi$ multiple bonds. In fact, the Nitrogen – Nitrogen triple bond in $N_2$ molecule has very high thermodynamic stability with a dissociation energy of $942kJ.mo{l}^{-1}$. This and other molecular orbital considerations account for the lack of allotropes of Nitrogen under normal conditions. However, it would be wrong to say that Nitrogen doesn’t have allotropes at all.
Gaseous nitrogen condenses into the $\beta$-hcp form at $-{210.01}^{\circ }C$. On freezing further, at temperatures below $-{237.6}^{\circ }C$ Nitrogen assumes the cubic α form. At room temperature and atmospheric pressure, gaseous $N_2$ does not have any other allotropes.