Noble gas

Helium

Helium (He) has atomic number 2. PubChem classifies it as noble gas.

Atomic number

2

Symbol

He

Atomic weight (source value)

4.00260

Electron configuration

1s2

Standard state

Gas

Electronegativity (Pauling)

Not provided

Melting point (K)

0.95

Boiling point (K)

4.22

Density (g/cm³)

0.0001785

Oxidation states

0

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.