15
P
Phosphorus
30.973762
Atomic Number: 15
Atomic Weight: 30.973762
Phase at Room Temperature: Solid
Element Classification: Non-metal
Period Number: 3 Group Number: 15
Group Name: Pnictogen
What's in a name? From the Greek word for light bearing, phosphoros.
Say what? Phosphorus is pronounced as FOS-fer-es.
History and Uses:
In what is perhaps the most disgusting method of discovering an element, phosphorus was first isolated in 1669 by Hennig Brand, a German physician and alchemist, by boiling, filtering and otherwise processing as many as 60 buckets of urine. Thankfully, phosphorus is now primarily obtained from phosphate rock (Ca3(PO4)2).
Phosphorus has three main allotropes: white, red and black. White phosphorus is poisonous and can spontaneously ignite when it comes in contact with air. For this reason, white phosphorus must be stored under water and is usually used to produce phosphorus compounds. Red phosphorus is formed by heating white phosphorus to 250°C (482°F) or by exposing white phosphorus to sunlight. Red phosphorus is not poisonous and is not as dangerous as white phosphorus, although frictional heating is enough to change it back to white phosphorus. Red phosphorus is used in safety matches, fireworks, smoke bombs and pesticides. Black phosphorus is also formed by heating white phosphorus, but a mercury catalyst and a seed crystal of black phosphorus are required. Black phosphorus is the least reactive form of phosphorus and has no significant commercial uses.
Phosphoric acid (H3PO4) is used in soft drinks and to create many phosphate compounds, such as triple superphosphate fertilizer (Ca(H2PO4)2·H2O). Trisodium phosphate (Na3PO4) is used as a cleaning agent and as a water softener. Calcium phosphate (Ca3(PO4)2) is used to make china and in the production of baking powder. Some phosphorus compounds glow in the dark or emit light in response to absorbing radiation and are used in fluorescent light bulbs and television sets.
