Iodine (I)
Iodine is the chemical element with atomic number 53 and symbol I. It is a reactive nonmetal in period 5, group 17, with a standard atomic weight of 126.9 u.
Key facts
- Z
- 53
- Atomic weight
- 126.9 u
- Category
- reactive nonmetal
- State at 298 K
- Solid
- Occurrence
- primordial
- Discovered
- 1811
- CAS
- 7553-56-2
Measured properties
| Property | Value | Source |
|---|---|---|
| Electronegativity | 2.66 | National Center for Biotechnology Information (NIH) |
| Melting point | 386.85 K | National Center for Biotechnology Information (NIH) |
| Boiling point | 457.55 K | National Center for Biotechnology Information (NIH) |
| Density stp | 4.93 g/cm³ | National Center for Biotechnology Information (NIH) |
| Atomic radius empirical | 198 pm | National Center for Biotechnology Information (NIH) |
| Ionization energy 1st | 1,008.4 kJ/mol | National Center for Biotechnology Information (NIH) |
| Electron affinity | 295.1 kJ/mol | National Center for Biotechnology Information (NIH) |
Electron configuration
- Noble gas notation
- [Kr] 4d¹⁰ 5s² 5p⁵
- Full notation
- 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p⁵
- Electrons per shell
- 2, 8, 18, 18, 7