Question

For which of the following molecules $p\pi -p\pi$ bonding is not possible under ordinary conditions.
Nitrogen, Phosphorus, Arsenic and Antimony.

• A. Nitrogen, Phosphorus
• B. Phosphorus, arsenic and antimony
• C. Nitrogen and antimony
• D. only phosphorus and arsenic

Answer 1

The correct option is B Phosphorus, arsenic and antimony

The given elements belong to the nitrogen family.
In the case of $N_2$, Nitrogen forms $p\pi -p\pi$ multiple bonds.
$N\equiv N$
1 bond is sigma and the remaining 2 bonds are $p\pi -p\pi$ bonds.

Other elements of group 15 do not form $p\pi -p\pi$ multiple bonds under normal conditions, because of the repulsions between the non-bonded electrons of the inner orbitals. Size also plays a role here.

There is no such repulsion in nitrogen atoms because of its small size and they have only $1s^2$ electrons in their inner orbital and hence, their p orbitals easily overlap to form $p\pi -p\pi$ multiple bonds.