53 I 126.9

Iodine

Reactive Nonmetal

Iodine (I) is a chemical element with atomic number 53, classified as a reactive nonmetal. At room temperature it is a solid. It was discovered in 1811 by Bernard Courtois.

Properties

Atomic number
53
Atomic mass
126.9 u
Category
Reactive Nonmetal
Group
17
Period
5
Block
p-block
Electron configuration
[Kr] 4d¹⁰ 5s² 5p⁵
Phase at STP
Solid
Density
4.93 g/cm³
Melting point
386.85 K (113.7 °C)
Boiling point
457.4 K (184.3 °C)
Electronegativity
2.66
Atomic radius
115 pm
Ionization energy
10.451 eV
Discovery
1811 · Bernard Courtois

Common uses

Antiseptics, table salt, medical imaging, photography

Did you know?

Essential for thyroid function and deficiency causes goiter.