053Reactive nonmetal · Group 17 · Period 5
Iodine
Iodine (I) is element 53, a reactive nonmetal in the p-block — group 17, period 5. It is a solid at room temperature with 5 electron shells (2, 8, 18, 18, 7) and an atomic mass of 126.904473 u.
- Atomic mass
- 126.9 u
- Phase · STP
- solid
- Melting
- 387 K · 114 °C
- Boiling
- 457 K · 184 °C
- Electronegativity
- 2.66
- Density
- 4.933 g/cm³
Photograph — Benjah-bmm27, Public domain, via Wikimedia Commons
Identity
- Atomic number
- 53
- Standard atomic weight
- 126.9 u
- Category
- Reactive nonmetal
- Group
- 17 · Halogens
- Period
- 5
- Block
- p-block
- Oxidation states
- +7, +5, +1, -1
Physical properties
- Melting point
- 387 K · 114 °C
- Boiling point
- 457 K · 184 °C
- Density
- 4.933 g/cm³
- Molar heat capacity
- —
- Atomic radius
- 198 pm
- Electron affinity
- 295.1531 kJ/mol
Atomic structure
53protons
74neutrons
53electrons
7valence e⁻
- Noble-gas notation
- [Kr] 4d10 5s2 5p5
- Full configuration
- 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p5
- Electrons per shell
- 2, 8, 18, 18, 7
Periodic trends
Where Iodine ranks across all 118 elements.
Ionization energies
Energy to remove each successive electron (kJ/mol).
1.0k1
1.8k2
3.2k3
Successive ionization energies (kJ/mol, log scale).
Discovery
- Discovered
- 1811
- Discovered by
- Bernard Courtois
- Named by
- —
- Appearance
- lustrous metallic gray, violet as a gas