Which of the following statements is wrong?

1. Single N—N bond is stronger than a single P—P bond.

2. ${\mathrm{PH}}_{3}$ can act as a ligand in the formation of coordination compound with transition elements.

3. ${\mathrm{NO}}_{2}$ is paramagnetic in nature.

4. Covalency of nitrogen in ${\mathrm{N}}_{2}{\mathrm{O}}_{5}$ is four.

Hint: Phosphorus forms allotropes but nitrogen does not.

The true statement is that a single N — N bond is weaker than a single P —P bond because of high interelectronic repulsion of the non-bonding electrons in N2, owing to the small bond length. This is why phosphorous shows allotropy but nitrogen does not.

The bond energy of N-N is 167 kJ mol-1, and for P-P is 201 kJ mol-1.

(i) PH3, acts as a ligand in the formation of coordination compound due to the presence of lone pair of electrons.

(i) ${\mathrm{NO}}_{2}$ is paramagnetic in nature due to the presence of one unpaired electron. The structure of ${\mathrm{NO}}_{2}$ is

(li) Covalency of nitrogen in ${\mathrm{N}}_{2}{\mathrm{O}}_{5}$ is 4