Write a note on allotropes of phosphorus.

(N/A) Phosphorus is found in many allotropic forms,the important ones being white,red,and black.
$I$. White phosphorus: White phosphorus is a translucent white waxy solid. It is poisonous,insoluble in water but soluble in carbon disulphide,and glows in the dark (chemiluminescence). It dissolves in boiling $NaOH$ solution in an inert atmosphere,giving $PH_{3}$ and sodium hypophosphite $(NaH_{2}PO_{2})$.
$P_{4} + 3NaOH + 3H_{2}O \rightarrow PH_{3} + 3NaH_{2}PO_{2}$
White phosphorus is less stable and therefore more reactive than the other solid phases under normal conditions because of angular strain in the $P_{4}$ molecule,where the angles are only $60^{\circ}$. It readily catches fire in air to give dense white fumes of $P_{4}O_{10}$.
$P_{4} + 5O_{2} \rightarrow P_{4}O_{10}$
It consists of discrete tetrahedral $P_{4}$ molecules.
$II$. Red phosphorus: When white phosphorus is heated at $573 \ K$ in an inert atmosphere for several days,red phosphorus is obtained.
Red phosphorus is polymeric,consisting of chains of $P_{4}$ tetrahedra linked together. It possesses an iron-grey lustre and is odourless,non-poisonous,and insoluble in water as well as in carbon disulphide.
When red phosphorus is heated under high pressure,a series of phases of black phosphorus is obtained. Chemically,red phosphorus is much less reactive than white phosphorus and it does not glow in the dark.