Correct Answer - 1
Black P has two forms `alpha`-black phosphorus and `beta`-black phosphorus. `alpha`-Black `P` is formed when red `P` is heated in a sealed tube at `803 K`. It can be sublimed in air and has opaque monoclinic or rhombohedral crystals. It does not oxidize in air.
`Beta`-Black`P` is prepared by heating white `P` at `473K` under high presure .It has a layer structure and does not burm in air upto `673K`.
