Chemical element · Atomic number 8
Oxygen
Oxygen in the periodic table: atomic number 8, electron configuration, atomic mass, physical data, oxidation states, media credit and visible sources.
Nonmetal
gaseous
15.999 u
Documented element sampleA labelled oxygen ampoule; the colorless gas is not visible through the glass.
Image credit: James St. John
Auto-oriented, limited to 1600 × 1200 pixels and re-encoded as WebP; the subject was not altered.
Atomic classification
Shell occupancy
Oxygen in the Bohr shell model
This shows the electron distribution of the neutral atom in a simplified shell model.
- K · n=1
- 2 electrons
- L · n=2
- 6 electrons
- Electron configuration
- [He]2s2 2p4
- Electrons per shell
- 2 · 6
- Group
- 16
- Period
- 2
- Block
- P
- Element category
- Nonmetal
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Physical and chemical properties
- Atomic mass
- 15.999 u
- Standard state
- gaseous
- Density
- 0.001429 g/cm³
- Melting point
- 54.36 K
- Boiling point
- 90.2 K
- Electronegativity
- 3.44 (Pauling)
- First ionisation energy
- 13.618 eV
- Oxidation states
- -2
- Discovery
- 1774
Safety and periodic classification
Safety
Safe handling cannot be inferred from Oxygen's position in the periodic table alone. Laboratory, classroom and disposal decisions must follow the documentation for the exact material and its safety data sheet.
Position and comparison
Oxygen is in period 2, group 16 and the P block. Its direct neighbours by atomic number are Nitrogen and Fluorine. The recorded Pauling electronegativity is 3.44. Periodic trends are compared only through the separately sourced neighbouring values.
Sources and scope
PubChem attributes element data to sources including IUPAC, NIST and IAEA. Quanta stores the referenced snapshot locally and leaves unknown values unavailable.