815.999OOxygen
Oxygen (O) — element 8reactive nonmetal · group 16, period 2
Oxygen is a chemical element with the symbol O and atomic number 8. It is a reactive nonmetal in group 16, period 2 of the periodic table (the p-block), with a standard atomic mass of 15.999 u. At room temperature (25 °C) oxygen is a gas.
💡 Known for: About 21% of the air; needed for breathing and burning, and the most abundant element in Earth's crust.
# Oxygen properties
| Symbol | O |
|---|---|
| Atomic number | 8 |
| Atomic mass | 15.999 u |
| Category | reactive nonmetal |
| Group | 16 |
| Period | 2 |
| Block | p-block |
| Electron configuration | [He] 2s² 2p⁴ |
| Full configuration | 1s² 2s² 2p⁴ |
| Electrons per shell | 2, 6 |
| Protons / electrons | 8 / 8 |
| State at 25 °C | gas |
| Melting point | 54.36 K (-218.8 °C, -361.8 °F) |
| Boiling point | 90.2 K (-182.9 °C, -297.3 °F) |
| Density | 1.429 g/L |
| Electronegativity (Pauling) | 3.44 |
| First ionization energy | 13.618 eV |
| Atomic radius | 48 pm |
| Discovered | 1774 |
# Electron configuration of oxygen
The electron configuration of oxygen is [He] 2s² 2p⁴, written out in full as 1s² 2s² 2p⁴. Its 8 electrons fill 2 shells as 2, 6, so the outermost shell holds 6 electrons. As a group 16 element, oxygen has 6 valence electrons.
# Related elements
NNitrogenprevious elementFFluorinenext elementSSulfurgroup 16SeSeleniumgroup 16TeTelluriumgroup 16PoPoloniumgroup 16LvLivermoriumgroup 16HHydrogenreactive nonmetalCCarbonreactive nonmetalPPhosphorusreactive nonmetal
# Oxygen FAQ
What is the atomic number of oxygen?
The atomic number of oxygen is 8: every oxygen atom has 8 protons in its nucleus. Its symbol is O.
What is the atomic mass of oxygen?
The standard atomic mass of oxygen is 15.999 u.
What is the electron configuration of oxygen?
Oxygen's electron configuration is [He] 2s² 2p⁴ (1s² 2s² 2p⁴), with 2, 6 electrons per shell.
Is oxygen a metal?
No. Oxygen is a reactive nonmetal, a nonmetal.
What is the melting point of oxygen?
Oxygen melts at 54.36 K (-218.8 °C, -361.8 °F) and boils at 90.2 K (-182.9 °C, -297.3 °F).
What is oxygen used for / known for?
About 21% of the air; needed for breathing and burning, and the most abundant element in Earth's crust.