Iodine (I)
Iodine (I) is element 53, a halogen. Atomic mass 126.90447, configuration [Kr] 4d¹⁰ 5s² 5p⁵. Properties, isotopes, oxidation states, uses and history, with an interactive 3D atom model.
Key facts
| Atomic number | 53 |
|---|---|
| Symbol | I |
| Standard atomic weight | 126.90447(3) |
| Category | Halogen |
| Group | 17 |
| Period | 5 |
| State at room temperature | Solid |
| Electron configuration | [Kr] 4d¹⁰ 5s² 5p⁵ |
| Valence electrons | 7 |
| Common oxidation states | -1, +1, +3, +5, +7 |
| Common ions | I⁻ |
| Electronegativity (Pauling) | 2.66 |
| First ionization energy | 1008 kJ/mol |
| Electron affinity | 295.2 kJ/mol |
| Atomic radius | 140 pm |
| Density | 4.933 g/cm³ |
| Melting point | 113.7°C |
| Boiling point | 184.40°C |
| Specific heat | 0.214 J/(g·°C) |
Natural isotopes
- I-127: Stable
Common uses
- Disinfectant (Betadine)
- Contrast media (X-ray)
- Thyroid nutrient
Where it matters
- Public Health (Iodized salt prevents goiter)
- Nuclear Safety (I-131 protection)
Hazards
- Vapors irritate eyes/lungs
- stains skin
History
| Discovered | 1811 |
|---|---|
| Discovered by | Bernard Courtois |
| Name | From Greek iodes (violet) |