53
I
Iodine
126.90447
Iodine (I)
HalogenGroup 17Period 5p-block-block
Iodine is a chemical element with symbol I and atomic number 53. The name is from Greek ἰοειδής ioeidēs, meaning violet or purple, due to the color of iodine vapor. Iodine and its compounds are primarily used in nutrition, and industrially in the production of acetic acid and certain polymers.
Latin name: Iodium
Atomic Number
53
Atomic Mass
126.90447 g/mol
Phase (STP)
Solid
Electron Config.
[Kr] 4d¹⁰ 5s² 5p⁵
General
SymbolI
Atomic Number53
Atomic Mass126.90447 g/mol
CategoryHalogen
Group17
Period5
Blockp-block
Electron Configuration[Kr] 4d¹⁰ 5s² 5p⁵
Valence Electrons7
Colourviolet-black metallic crystals
Appearancelustrous metallic gray, violet as a gas
CAS NumberCAS7553-56-2
Physical Properties
Phase (STP)Solid
Density4.93 g/cm³
Melting Point113.70°C · 236.66°F · 386.85 K
Boiling Point184.40°C · 363.92°F · 457.55 K
Atomic Properties
Atomic Radius115 pm
Electronegativity2.66 Pauling
Ionization Energy1008 kJ/mol
Oxidation States+7, +5, +3, +1, -1
Ion ChargeI-/I+
Crystal Structure
Crystal Structureorthorhombic
Mechanical Properties
Mohs Hardness2
Nuclear & Hazards
Half-lifestable
Abundance
In Universe0.00003%
In Sun0.000025%
In Earth's Crust0.000049%
In Oceans0.0002%
In Humans0.0002%
Discovery & History
Discovery Year1811
Discovered ByBernard Courtois
Country of DiscoveryFrance
Isotopes of Iodine
| Isotope | Abundance | Half-life | Decay |
|---|---|---|---|
| I-127 | 100% | Stable | — |
| I-129 | — | 1.57 × 10⁷ years | β⁻ |
| I-131 | — | 8.025 days | β⁻ |