Nonmetal

Selenium

Selenium (Se) has atomic number 34. PubChem classifies it as nonmetal.

Atomic number

34

Symbol

Se

Atomic weight (source value)

78.97

Electron configuration

[Ar]4s2 3d10 4p4

Standard state

Solid

Electronegativity (Pauling)

2.55

Melting point (K)

493.65

Boiling point (K)

958

Density (g/cm³)

4.809

Oxidation states

+6, +4, -2

Understanding this entry

Atomic number is the number of protons in the nucleus. Properties are reference values and may depend on conditions and measurement conventions. An atomic weight is not the mass of every isotope. For elements without a standard atomic weight, a source may report an isotope mass number. Blank source values are shown as unavailable rather than estimated.

Further reading and reference: NIH PubChem source dataset ↗. Values and educational summaries are not a substitute for specialised advice.