049Post-transition metal · Group 13 · Period 5
Indium
Indium (In) is element 49, a post-transition metal in the p-block — group 13, period 5. It is a solid at room temperature with 5 electron shells (2, 8, 18, 18, 3) and an atomic mass of 114.8181 u.
- Atomic mass
- 114.8 u
- Phase · STP
- solid
- Melting
- 430 K · 157 °C
- Boiling
- 2345 K · 2072 °C
- Electronegativity
- 1.78
- Density
- 7.31 g/cm³
Photograph — Jurii, CC BY 3.0 <https://creativecommons.org/licenses/by/3.0>, via Wikimedia Commons, source: http://images-of-elements.com/indium.php
Identity
- Atomic number
- 49
- Standard atomic weight
- 114.8 u
- Category
- Post-transition metal
- Group
- 13
- Period
- 5
- Block
- p-block
- Oxidation states
- +3
Physical properties
- Melting point
- 430 K · 157 °C
- Boiling point
- 2345 K · 2072 °C
- Density
- 7.31 g/cm³
- Molar heat capacity
- 26.74 J/(mol·K)
- Atomic radius
- 193 pm
- Electron affinity
- 37.043 kJ/mol
Atomic structure
49protons
66neutrons
49electrons
3valence e⁻
- Noble-gas notation
- [Kr] 4d10 5s2 5p1
- Full configuration
- 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p1
- Electrons per shell
- 2, 8, 18, 18, 3
Periodic trends
Where Indium ranks across all 118 elements.
Ionization energies
Energy to remove each successive electron (kJ/mol).
558.31
1.8k2
2.7k3
5.2k4
Successive ionization energies (kJ/mol, log scale).
Discovery
- Discovered
- 1863
- Discovered by
- Ferdinand Reich
- Named by
- —
- Appearance
- silvery lustrous gray