Periodic Table
8
O
15.999
Oxygen
NonmetalParamagnetic O₂ (MOT); supports combustion; second most electronegative.
Electronic Configuration
1s² 2s² 2p⁴or1s² 2s² 2p⁴
Electron shells
2e⁻n=1
6e⁻n=2
Properties
Atomic number
8
Atomic mass
15.999 u
Category
Nonmetal
Block / Group / Period
p · 16 · 2
Valence electrons
6
Oxidation states
-2, -1
Electronegativity
3.44
Atomic radius
48 pm
Ionization energy
1314 kJ/mol
Electron affinity
141 kJ/mol
Melting point
54 K / -219 °C
Boiling point
90 K / -183 °C
Density
0.001429 g/cm³
State at 25 °C
gas
JEE / NEET notes
- O₂ is paramagnetic — explained only by Molecular Orbital Theory (2 unpaired e⁻).
- Forms strong H-bonds → anomalously high b.p. of H₂O.
- O₃ (ozone) is a powerful oxidiser; bent molecule, resonance.
Exceptions
- • Paramagnetism of O₂ is the classic MOT exception.
Uses
Steel making · Medical oxygen · Rocket oxidiser · Welding
Important compounds
H₂OH₂O₂O₃CO₂
Did you know? Liquid oxygen is pale blue and is attracted to a magnet.
Personal Notes
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