Phosphorus does not have a formula, in its pure form it is an element which contains only atoms of Phosphorus and nothing else. The chemical symbol for Phosphorus is P.
Added:
is the adjective of compounds related to the phosphiteanion: PO33-
or to the acid H3PO3 , phosphorous acid.
Formula: P4
The chemical symbol (not formula) of phosphorous is P; the chemical symbol (not formula) of chlorine is Cl.
Also phosphorous is the ion (PO3)3-.
Formula: PCl3
You think probable to the unstable compound P4S2.
Formula: P2O3
The formula (symbol) for aluminum is Al. The symbol for phosphorous is P. The formula for aluminum combined with phosphorous is AlP (aluminum phosphide).
P4Se3
PCl3
Phosphorous Trioxide
Phosphorous Hydride = PH3
Phosphorus pentachloride is a chemical compound with the formula PCl5.