Nitrogen because of its small size and high electronegativity forms `ppi-ppi-` multiple bonds.Therefore, it exists as a diatomic molecule having a triple bond between the two `N`-atoms.Phosphorus, on the other hand, due to its larger size and lower electronegativity usually does not form `ppi-ppi` multiple bonds with itself.Instead it prefers to form `P-P` single bonds and hence it exists as tetrahedral `P_(4)` molecules.
