Question

Nitrogen forms $N_2$ but phosphorus is converted into $P_4$ from $P_2$. The reason for this is:

• A. triple bond is present between phosphorus atoms.
• B. $p\pi -p\pi$ bonding is weak.
• C. $p\pi -p\pi$ bonding is strong.
• D. multiple bond is formed easily.

Answer 1

Answer: (B)

$p\pi -p\pi$ bonding is weak.

Due to larger atomic size P is unable to form pi bond and so it is tetra-atomic in which each P atom is linked with 3 other P atoms by 3 sigma bonds.

But, due to smaller atomic size N forms 1 sigma and 2 pi bonds i.e. triple bonds with other N atom and exists as diatomic molecules. Hence the bonding is responsible for that.

Phosporous form $P_4$ because in $P_2$ $p\pi$-$p\pi$ bond is weaker.

Hence option B is correct.