Oxygen
The reactive gas that powers respiration and combustion.
Inside the Oxygen atom
Switch between Bohr and Quantum Cloud modes to compare a simple teaching model with a more realistic probability-based view, and follow the guided tour to explore the Oxygen atom step by step.
Electron configuration
[He] 2s2 2p4
A neutral Oxygen atom has 8 electrons (equal to its proton count). Choosing a different isotope above changes only the neutron count.
Shell distribution
Electrons fill inner shells before outer ones; the outermost (valence) shell drives the element's chemistry.
Physical & atomic properties
- State (room temp)
- Gas
- Melting point
- 54 K (-219 °C)
- Boiling point
- 90 K (-183 °C)
- Density
- 0.001429 g/cm³
- Electronegativity
- 3.44 Pauling
- Atomic radius
- 60 pm
- 1st ionization energy
- 1314 kJ/mol
- Category
- Reactive nonmetals
Discovery & naming
- Discovered
- 1774
- Discovered by
- Joseph Priestley and Carl Wilhelm Scheele
- Origin of name
- Greek 'oxys genes', meaning acid-forming.
Notable uses
Respiration, steelmaking, welding, and medical support.
Where Oxygen comes from
Stellar fusion and dying stars
Made when carbon captures a helium nucleus inside massive stars, then scattered when those stars explode.
Simplified origin map — many elements form through more than one astrophysical pathway.
Summary
- Atomic number
- 8
- Atomic mass
- 15.999
- Category
- Reactive nonmetals
- Group · Period
- 16 · 2
- Block
- p-block
- Shells
- 2 · 6