Nitrogen forms N₂, phosphorus also farms P₂ but is readily converted to P₄ because:

triple bond is present in phosphorus atoms

$\mathrm{p\pi }‐\mathrm{p\pi }$ bonding in phosphorus is weak

$\mathrm{p\pi }‐\mathrm{p\pi }$ bonding in phosphorus is strong

multiple bonds are formed easily in phosphorus