Indium (In): Electron Configuration, Properties and Uses
Indium (In): Electron Configuration, Properties and Uses
Electron configuration [Kr] 5s2 4d10 5p1 · group 13 · period 5 · Ar 114.82
Indium data
- Atomic number
- 49
- Relative atomic mass
- 114.82
- Group
- 13
- Period
- 5
- Block
- p
- Category
- Post-transition metal
- Electron configuration
- [Kr] 5s2 4d10 5p1
- Full configuration
- 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p1
- Electrons per shell
- 2, 8, 18, 18, 3 (K L M N O)
- Valence electrons
- 3
- Electronegativity (Pauling)
- 1.78
- First ionisation energy
- 5.786 eV
- Atomic radius (van der Waals)
- 193 pm
- State at room temperature
- Solid
- Melting point
- 157 °C
- Boiling point
- 2072 °C
- Density
- 7.31 g/cm³
- Common oxidation states
- +3
- Discovered
- 1863
Source: PubChem (NIH, accessed 13 Nov 2026); atomic mass: IUPAC standard atomic weight.
Electron shell diagram
K 2 · L 8 · M 18 · N 18 · O 3
Orbital diagram (outer electrons)
About indium
With atomic number 49, indium (In) has 49 protons in its nucleus and 49 electrons as a neutral atom. It is a post-transition metal in group 13, period 5, p-block. The element was discovered in 1863. Indium is a solid at room temperature, melting at 157 °C and boiling at 2072 °C.
Indium electron configuration
The electron configuration of indium is 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p1, or in short [Kr] 5s2 4d10 5p1. Its electrons occupy 5 shells: K = 2, L = 8, M = 18, N = 18, O = 3. Indium has 3 valence electrons in the O shell (5s2 5p1), which is why it sits in group 13. When it forms cations, electrons leave the outermost subshell first: In3+ = [Kr] 4d10.
Filling order: 1s2(2) → 2s2(4) → 2p6(10) → 3s2(12) → 3p6(18) → 4s2(20) → 3d10(30) → 4p6(36) → 5s2(38) → 4d10(48) → 5p1(49)
Uses of indium
In industry and the laboratory, indium turns up in many places, for example ITO (indium tin oxide) coatings on touchscreens and solar cells, and low-temperature solders. For research and analysis you can browse indium compounds in the AMI Scientific catalogue.
Safety
Bulk indium has low toxicity. The main hazards are its dust and salts, so always check the SDS of the compound you use. Always read the safety data sheet (SDS) before working with a chemical.
Other elements in group 13
Frequently asked questions
What is the electron configuration of indium?
The electron configuration of indium (In, atomic number 49) is 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p1, or [Kr] 5s2 4d10 5p1 in short. By shell: 2, 8, 18, 18, 3.
How many valence electrons does indium have?
Indium has 3 valence electrons.
Which group and period is indium in?
Indium is in group 13, period 5, p-block.
What is the atomic mass of indium?
The relative atomic mass of indium is 114.82. Use it to calculate molar mass with the molar mass calculator.
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