Draw the structure of white phosphorus and red phosphorus. Which one of these two types of phosphorus, is more reactive and why ?
Or Which allotrope of phosphorus is more reactive and why?
Or Why is red phosphorus less reactive than white phosphorus.
Or Draw the structural difference between white and red phosphorus.

Explanation

Both white and red phosphorus consist of `P_(4)` tetrahedra. In white phosphorus, the various `P_(4)` molecules are held together by weak van der Waals forces of attraction. In each `P_(4)` molecule, the PPP angle is only `60^(@)` (Fig. 11.31, page 11/127) which is much smaller than the normal tetrahedral angle of `109^(@)-28`. As a result, there is considerable angle strain. Due to weaker forces of attraction and considerable angle strain, white phsphorus is very reactive.
In contrast, in red phosphorus, these `P_(4)` tetrahedra are joined together throughi covalent bonds to give polymeric structure (Fig. 11.32, page 11/129).
Since it is difficult to break strong covalent bond as compared to weak van der Waals forces of attraction, therefore, white phosphorus is more reactive than red phosphorus.