Answer
The general structure of red phosphorus is similar to that of white phosphorus, except that one of the bonds between two phosphorus atoms in the tetrahedron is broken. The two phosphorus atoms then link to other phosphorus atoms, making chains that vary in structure. Red phosphorus is neither as reactive nor as toxic as white phosphorus, and even though it is also flammable, it can be stored in air.
Work Step by Step
When heated to about $300^{\circ} C$ in the absence of air, white phosphorus slightly changes its structure to a different allotrope called red phosphorus, which is amorphous.
The general structure of red phosphorus is similar to that of white phosphorus, except that one of the bonds between two phosphorus atoms in the tetrahedron is broken. The two phosphorus atoms then link to other phosphorus atoms, making chains that vary in structure.
Black phosphorus is obtained by heating white phosphorus under pressure. This form of phosphorus is the most thermodynamically stable form, and therefore the least reactive. Black phosphorus has a layered structure similar to that of graphite.
