Catenation is the bonding of atoms of the same element into a series to form a chain. Catenation is much more common in phosphorous compounds than in nitrogen compounds.

This is because of the relative weakness of the N−N single bond as compared to the P−P single bond. Since nitrogen atom is smaller, there is greater repulsion of electron density of two nitrogen atoms, thereby weakening the N−N single bond. This is the reason why Nitrogen shows catenation properties less than phosphorous.

Phosphorous has larger atomic size because of which it has less repulsion of electron density of two phosphorous atoms and hence P-P single bond is stronger.