Indium Facts

Indium Chemical & Physical Properties

Photograph of the metal indium, with a penny to indicate the size of the sample.
U.S. Geological Survey

Indium Basic Facts

Atomic Number: 49

Symbol: In

Atomic Weight: 114.818

Discovery: Ferdinand Reich and T. Richter 1863 (Germany)

Electron Configuration: [Kr] 5s2 4d10 5p1

Word Origin: Latin indicum. Indium is named for the brilliant indigo line in the spectrum.

Isotopes: Twenty-three isotopes of indium are known. Only one stable isotope, In-127, occurs naturally.

Properties: The melting point of indium is 156.61 °C, boiling point is 2080 °C, specific gravity is 7.31 (20 °C), with a valence of 1, 2, or 3.

Indium is a very soft, silvery-white metal. The metal has a brilliant luster and emits a high pitched sound when bent. Indium wets glass. Indium may be toxic, but further research is required to assess its effects.

Uses: Indium is used in low melting point alloys, making bearing alloys, transistors, thermistors, photoconductors, and rectifiers. When plated or evaporated onto glass, it forms a mirror as good as that formed by silver, but with superior resistance to atmospheric corrosion.

Sources: Indium often is associated with zinc materials. It is also found in iron, lead, and copper ores.

Element Classification: Metal

Indium Physical Data

Density (g/cc): 7.31

Melting Point (K): 429.32

Boiling Point (K): 2353

Appearance: very soft, silvery-white metal

Atomic Radius (pm): 166

Atomic Volume (cc/mol): 15.7

Covalent Radius (pm): 144

Ionic Radius: 81 (+3e)

Specific Heat (@20°C J/g mol): 0.234

Fusion Heat (kJ/mol): 3.24

Evaporation Heat (kJ/mol): 225.1

Debye Temperature (K): 129.00

Pauling Negativity Number: 1.78

First Ionizing Energy (kJ/mol): 558.0

Oxidation States: 3

Lattice Structure: Tetragonal

Lattice Constant (Å): 4.590


References: Los Alamos National Laboratory (2001), Crescent Chemical Company (2001), Lange's Handbook of Chemistry (1952), CRC Handbook of Chemistry & Physics (18th Ed.)


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Helmenstine, Anne Marie, Ph.D. "Indium Facts." ThoughtCo, Mar. 10, 2017, Helmenstine, Anne Marie, Ph.D. (2017, March 10). Indium Facts. Retrieved from Helmenstine, Anne Marie, Ph.D. "Indium Facts." ThoughtCo. (accessed June 19, 2018).