Question

What are the forms of black phosphorus?

Answer 1

Black phosphorus:

• It is an allotrope of phosphorus.
• It is the least reactive form of phosphorus.

Black phosphorous is categorized into two types that are discussed below:

1. Alpha-black phosphorus:

• It consists of rhombohedral crystals.

Reaction of Alpha-black phosphorus:

• When red phosphorus is heated at $803\mathrm{K}$, alpha black phosphorus is formed.
• The chemical equation can be depicted as:

$\mathrm{Red}\mathrm{phosphorus}\stackrel{803\mathrm{K}}{\to }\mathrm{\alpha }-\mathrm{black}\mathrm{phosphorus}$

2. Beta-black phosphorus:

• It consists of layered crystals arranged in the form of sheets.

Reaction of Beta-black phosphorus:

• When white phosphorus is heated under high pressure and at $473\mathrm{K}$, beta black phosphorus is formed.
• The chemical equation can be depicted as:

$\mathrm{White}\mathrm{phosphorus}\stackrel{473\mathrm{K}}{\to }\mathrm{\beta }-\mathrm{black}\mathrm{phosphorus}$