Why white phosphorus is more reactive than red phosphorus?

Explanation

White phosphorus consists of discrete tetrahedral `P_4` molecules in which the P-P-P angle is `60^@`. The less stability and hence more reactivity of white phosphorus than the other solid phases (like red phosphorus) under normal conditions in due to angular strain in the `P_4` molecule where all the P-P-P angles are only `60^@`