Phosphorus is a chemical element with symbol P and atomic number 15. As an element, phosphorus exists in two major forms— white phosphorus and red phosphorus —but due to its high reactivity, phosphorus is never found as a free element on Earth.Instead phosphorus-containing minerals are almost always present in their maximally oxidised state, as inorganic phosphate rocks.hite phosphorus glows in the dark (when exposed to oxygen) with a very faint tinge of green and blue, is highly flammable and pyrophoric (self-igniting) upon contact with air and is toxic (causing severe liver damage on ingestion). Owing to its pyrophoricity, white phosphorus is used as an additive in napalm.