Due to smaller size, the lone pairs of electronc on the two N-atoms repel the bond pair of N-N bond. In contrast, because of comparatively larger size of P, the lone pairs of electrons on the two P atoms do not repel the bond pair of the P-P bond to the same extent. As a result, N-N single bond is weaker `(159kJmol^(-1))` than P-P single bond `(213kJmol^(-1))`. Consequently, nitrogen shows little tendency for catenation or phosphorus has greater tendency for catenation.
