Element 8
Oxygen (O)
Oxygen (O) is element 8 of the periodic table, a reactive nonmetal in period 2, group 16 (p-block) with an atomic mass of 15.999 and is a gas at standard conditions.
At a glance
- Atomic number
- 8
- Symbol
- O
- Atomic mass
- 15.999 u
- Category
- Reactive nonmetals
- Period
- 2
- Group
- 16
- Block
- p-block
- Phase at STP
- gas
Electron structure
- Electron configuration
- 1s2 2s2 2p4
- Shorthand configuration
- [He] 2s2 2p4
- Electrons per shell
- 2, 6
- Oxidation states
- -2, -1, +1, +2
Physical properties
- Melting point
- 54.36 K (-218.79 °C)
- Boiling point
- 90.2 K (-182.95 °C)
- Density
- 0.001429 g/cm³
- Phase
- gas
Atomic properties
- Electronegativity (Pauling)
- 3.44
- Atomic radius
- 48 pm
- Covalent radius
- 66 pm
- Van der Waals radius
- 152 pm
- First ionization energy
- 1314 kJ/mol
- Electron affinity
- 141 kJ/mol
Notable isotopes
| Isotope | Mass | Abundance | Stability |
|---|---|---|---|
| O-16 | 15.99491 | 99.76% | Stable |
Common uses
- Respiration
- Steel manufacturing
- Medical therapy
- Water treatment
Discovery
- Year
- 1774
- Discovered by
- Joseph Priestley, Carl Wilhelm Scheele
- Country
- England/Sweden
Frequently asked questions
- Is oxygen a metal?
- No. Oxygen is a nonmetal, classified as a reactive nonmetal on the periodic table.
- How many protons does oxygen have?
- Oxygen has 8 protons. Its atomic number is 8, which is also the number of electrons in a neutral atom of oxygen.
- What group and period is oxygen in?
- Oxygen is in group 16 and period 2 of the periodic table, in the p-block.
- What is the atomic mass of oxygen?
- The atomic mass of oxygen is 15.999 u (unified atomic mass units).
Keep exploring
Oxygen's row is on the printable element property sheet, and its tile is on the periodic table wall chart - the same numbers as above, laid out for A4 or A3 paper.