Electron configuration and elemental properties of indium.
Electron configuration and elemental properties of indium.
Credit: Greg Robson/Creative Commons, Andrei Marincas Shutterstock
Atomic Number: 49
Atomic Symbol: In
Atomic Weight: 114.818
Melting Point: 313.88 F (156.6 C)
Boiling Point: 3,761.6 F (2,072 C)

Word origin: Indium is named after the brilliant indigo line in its spectrum.

Discovery: Indium was isolated in 1863 by German chemists Ferdinand Reich and Hieronymous Theodor Richter.

Properties of indium

Indium is a soft silvery-white metal. It is one of the post-transition metals, which tend to be softer and conduct more poorly than the transition metals. It’s one of the softest metals known. Its main spectral lines are a bright indigo blue. [See Periodic Table of the Elements]

The metal has a very low melting and boiling point making it ideal for soldering because it remains workable at low temperatures. One of indium’s most unusual properties is that it has a “tin cry” or a sound that resembles a scream when it’s bent.

A 2-by4.5-cm ingot of indium weighs 40 grams.
A 2-by4.5-cm ingot of indium weighs 40 grams.
Credit: Images of elements

Sources of indium     

Indium is relatively rare in the Earth, and is typically found in zinc ores. Until 1924, the entire world's supply of the element consisted of one gram. Today, about 4 million troy ounces of indium are produced annually. Canada, China and Russia are major producers. It’s also found in some lead, copper and iron ores.

Uses of indium

Indium is useful as an alloy material. The metal is used to make low melting alloys and bearing alloys. It’s also used in germanium transistors, rectifiers, thermistors, and photoconductors. A particular alloy of indium and gallium can be liquid at room temperature. Indium’s unique properties allow it to be evaporated onto glass to form a mirror or plated onto metal.

Indium tin oxide is used to make transparent conductors. A fluid alloy of gallium and indium shows promise as "self-healing" wire.

(Source: Los Alamos National Laboratory)