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

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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