Iodine

Atomic number

53

Atomic mass (u)

126.9045

Category

Halogen

Standard state

Solid

Melting point

113.7 °C (386.85 K)

Boiling point

184.4 °C (457.55 K)

Density (g/cm³)

4.93

Electronegativity (Pauling)

2.66

Electron configuration

[Kr]5s2 4d10 5p5

Oxidation states

+7, +5, +1, -1

Atomic radius (pm)

198

First ionization energy (eV)

10.451

Discovery & recognition

Discovery year / period (PubChem)

1811

Discovery credited to (RSC)

Bernard Courtois

Date or period recorded by RSC

1811

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.

“Iodine is found in seawater, as iodide.”

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.