Iodine
Iodine (碘, symbol I) is chemical element number 53, a Halogen in period 5, group 17 of the periodic table, with a standard atomic weight of about 126.9. Lustrous, purple-black halogen. Essential for thyroid hormones.
Properties
| Atomic number | 53 |
|---|---|
| Symbol | I |
| Atomic mass | 126.9 u |
| Category | Halogen |
| Period | 5 |
| Group | 17 |
| Electron configuration | [Kr] 4d¹⁰ 5s² 5p⁵ |
| Electronegativity | 2.66 |
| Covalent radius | 139 pm |
| Density | 4.93 g/cm³ |
| Melting point | 386.85 K |
| Boiling point | 457.4 K |
| Discovery | Bernard Courtois, 1811 |
Overview
Lustrous, purple-black halogen. Essential for thyroid hormones. Element 53, Iodine (I), is a Halogen found in period 5, group 17. As a halogen it is a reactive nonmetal that readily gains one electron to form a −1 ion.
Its electron configuration is [Kr] 4d¹⁰ 5s² 5p⁵, with 7 electrons in the outer shell, and an electronegativity of about 2.66 (Pauling). Around 25 °C it is usually a solid; it melts near 386.85 K (113.7 °C), boils near 457.4 K (184.3 °C), has a density around 4.93 g/cm³.
In industry and daily life it turns up in Medical / Pharma and Agriculture / Fertiliser. On the safety side, it carries a moderate hazard rating. It was first described by Bernard Courtois in 1811. Use the comparison tool to line it up against other elements.
Electron shells
Electrons per shell: 2 · 8 · 18 · 18 · 7
Main uses
- Medical / Pharma
- Agriculture / Fertiliser
Hazard
Compounds containing Iodine
No compounds in this knowledge base contain Iodine yet.
Data sources
Atomic mass uses IUPAC (CIAAW) standard atomic weights; the covalent radius is from Cordero et al. (2008). Verify on the RSC Periodic Table, PubChem and Wikipedia. Educational reference only.