Atomic number: 15

Symbol: P

Category: non-metal

Density at 25°C: solid, varies from 1.823 - 2.69

This is an other element essential to life, but it is so reactive in nature that it has to combine with another element. It occurs in two major forms when isolated: white and red.  White is considered the most important form becuase it tends to react most spectacularly. 

White phosphorus in mineral oil. image: adapted from wikipedia


Phosphorous often occurs as a tetra atomic form of P4 molecules

Use, natural applications or common combinations: 

  • in life, DNA, RNA and ATP, 
  • Important in steel production
  • matches

Basic characteristics:

  • Standard atomic weight: 30.973 762(2)
  • Melting point: (white) 44.2 °C
  • Boiling point: (white) 280.5 °C
  • Radioactivity: most are stable
    • The longest-lived synthetic radioactive isotopes are 33P with a half-life of 25.34 days and 32P with a half-life of 14.263 days