Atomic number 8
Oxygen
Nonmetal
In the real world
Quick facts
- Atomic mass
- 15.999
- Group
- 16
- Period
- 2
- State (STP)
- gas
- Electronegativity
- 3.44
- Common ox. states
- -2, -1
Properties
Electron configuration
[He] 2s² 2p⁴
- Ionization energy
- 1313.9 kJ/mol
- Electron affinity
- 141.0 kJ/mol
- Melting point
- 54.36 K (-218.8 °C)
- Boiling point
- 90.19 K (-183.0 °C)
How dangerous is it?
2/5 · Caution
The gas you breathe is not flammable itself, but in pure or pressurized form it makes everything else burn far faster and hotter.
- OxidizerImmediate
It feeds combustion, so materials that barely burn in air can ignite violently in pure oxygen. (the hazard is pure or pressurized oxygen, not ordinary air)
Fittings are kept free of oil and grease, and tanks are stored away from fuels.
How it bonds
Oxygen has 6 valence electrons and forms 2 bonds, leaving 2 lone pairs. Those lone pairs squeeze the bond angle in water (104.5°) and let oxygen accept hydrogen bonds - the reason water is liquid, ice floats, and proteins fold. Oxygen also doubles up (O=C in CO₂, O=O in O₂).
Element Lore
Stories, history, and chemistry behind Oxygen.
Read Oxygen's lore →Where you meet it
Compounds featuring this element
- Carbon dioxideCO₂
- FormaldehydeCH₂O
- Hydrogen peroxideH₂O₂
- OxygenO₂
- Sulfur dioxideSO₂
- WaterH₂O
