Atomic number 8
Oxygen
Nonmetal
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 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.
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