Tools · Chemistry

Oxygen (O)

Oxygen (O) is element 8 of the periodic table, a nonmetal in period 2 and group 16. Its standard atomic weight is 15.999, so one mole of oxygen atoms has a mass of 15.999 g. At room temperature it is a gas; it melts at -218.79 °C and boils at -182.95 °C.

8 O Oxygen 15.999

Period 2, group 16 · Nonmetal

← N Nitrogen F Fluorine →

Atomic number	8
Symbol	O
Standard atomic weight	15.999
Molar mass	15.999 g/mol
Category	Nonmetal
Group	16
Period	2
Block	p-block
Electron configuration	[He] 2s² 2p⁴
Oxidation states	−2
Electronegativity (Pauling)	3.44
Atomic radius (van der Waals)	152 pm
First ionisation energy	13.618 eV (1313.9 kJ/mol)
Electron affinity	1.461 eV
State at room temperature	Gas
Melting point	54.36 K (-218.79 °C)
Boiling point	90.2 K (-182.95 °C)
Density	1.429 g/L
Discovered	1774

Group 16

S · Sulfur Se · Selenium Te · Tellurium Po · Polonium Lv · Livermorium

Calculate with Oxygen

Molar mass of O Balance an equation Grams, moles and particles Whole periodic table

Atomic weight: IUPAC CIAAW standard atomic weight. Other properties: PubChem (U.S. National Library of Medicine, public domain). Values such as melting point and radius depend on how they were measured; check a data book for precise work.