ElementsWhat is indium?
Indium is a very soft, silvery metal. A bar of it gives a faint cry when bent.
What is indium used for?
Indium tin oxide, the clear coating that carries electricity on touch screens and flat displays. Also solders.
Where the name comes from
From the indigo-blue line in its spectrum.
Key facts
- Symbol
- In
- Atomic number
- 49
- Atomic mass
- 114.818 u
- Family
- Post-transition metal
- Period
- 5
- Group
- 13
- Block
- p
- State at room temperature
- Solid
- Melting point
- 156.6 °C (429.75 K, 314 °F)
- Boiling point
- 2,072 °C (2,345 K, 3,761 °F)
- Density
- 7.31 g/cm³
- Electrons per shell
- 2, 8, 18, 18, 3
- Electron configuration
- [Kr]5s2 4d10 5p1
- Common oxidation states
- +3
- Electronegativity (Pauling)
- 1.78
- First ionisation energy
- 5.786 eV
- Electron affinity
- 0.3 eV
- Atomic radius (van der Waals)
- 193 pm
- Discovered
- 1863
Place in the periodic table
Indium is element number 49. It sits in period 5 (row 5) of the periodic table, in group 13 (column 13), and belongs to the p-block. Just before it comes cadmium (48), and just after it comes tin (50). In the same column, gallium is above it and thallium is below it. Elements in one column tend to behave alike.
Family: Post-transition metals.
Physical properties
At room temperature indium is a solid. It melts at 156.6 °C and boils at 2,072 °C, so it stays liquid over a range of 1,915 degrees. Its density is 7.31 grams per cubic centimetre, so a one-litre block would weigh about 7.31 kilograms. By density it ranks 43rd among the 96 elements with a measured value.
Inside the atom
An atom of indium has 49 protons in its nucleus and, when neutral, 49 electrons around it. The electrons are arranged in 5 shells: 2, 8, 18, 18, 3. The outermost shell holds 3 electrons. Written in full, the electron configuration is [Kr]5s2 4d10 5p1.
Its electronegativity on the Pauling scale is 1.78. This number shows how strongly an atom pulls shared electrons towards itself: fluorine, the strongest, is 3.98. Removing one electron from an atom takes 5.786 electronvolts (about 558 kilojoules per mole). One mole of indium weighs 114.818 grams, so a single gram contains about 5.24 × 1021 atoms.
The ring picture is a simple model that only counts the electrons in each shell. Real atoms do not look like this.
Next steps
- Work out the weight of a compound that contains indium with the molar mass calculator.
- Compare it with every other element in the sortable list.
- Test yourself with the symbol quiz.
Figures on this page are from PubChem (U.S. National Library of Medicine), as downloaded on 11 November 2026. See About and data sources.