Atomic number: 8

Symbol: O

Category: non metal

Density at 25°C: gas

Another more familiar element. But it is naturally unstable and like nitrogen, prefers to hang together as a pair of atoms as O2. which is familiar to us as something essential to life and breathing (oxidative respiration).


A bluish tinge from an electric discharge tube containing oxygen. image: wikipedia

Use, natural applications or common combinations: 

  • used in metabolism for making energy molecules.
  • basis of ozone O3 a strong oxidising agent.

Basic characteristics:

  • Standard atomic weight: [15.99903; 15.99977] why this variation?
  • Melting point: -218.79 °C
  • Boiling point: -182.95 °C
  • Radioactivity: almost all stable
    • others all have very short half lifes, longest is 15O  at 122 seconds used in PET scanners.