White phosphorous is the most volatile, unstable, toxic allotrope. Each atom in a tetrahedral P4 molecule is connected to the other atoms by a single bond. It is essential for life because it is a part of RNA, DNA, ATP, and all cell membranes. Under light and heat, it can turn into red phosphorous, which is a polymer. Phosphoric acids are used as fertilizers. They are also used in detergents. It is also part of calcium phosphate salts that harden bones.