Hydrogen

Atomic number

1

Atomic mass (u)

1.0080

Category

Nonmetal

Standard state

Gas

Melting point

-259.34 °C (13.81 K)

Boiling point

-252.87 °C (20.28 K)

Density (g/cm³)

0.00008988

Electronegativity (Pauling)

2.2

Electron configuration

1s1

Oxidation states

+1, -1

Atomic radius (pm)

120

First ionization energy (eV)

13.598

Discovery & recognition

Discovery year / period (PubChem)

1766

Discovery credited to (RSC)

Henry Cavendish

Date or period recorded by RSC

1766

Discovery place

Not supplied in the structured record; see the RSC history source.

An ancient date does not identify a first human discovery. Different references may date observation, isolation and formal recognition differently.

Natural occurrence & production

The creation of an element’s nuclei and its concentration into terrestrial deposits are different processes. The occurrence note below concerns its presence or production on Earth; it is not a complete account of nucleosynthesis.

“Hydrogen is easily the most abundant element in the universe.”

Royal Society of Chemistry · occurrence excerpt ↗

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Reference values are not product specifications. Blank values have not been estimated. For superheavy elements, some properties and family assignments are theoretical or incompletely measured.