Indium
Definition and meaning of Indium in chemistry.
![Indium element card: symbol In, atomic number 49, atomic mass 114.82, electron configuration [Kr] 4d¹⁰ 5s² 5p¹, oxidation states +3, Post-transition metal, group 13, period 5, solid at room temperature.](/assets/images/terms/indium-chemical-element.webp)
Indium is a very soft, silvery-white post-transition metal identified by the chemical symbol In and atomic number 49. Because this rare element is extremely malleable, you can easily bend it or cut it with a simple knife. Scientists discovered indium in 1863 by studying its light emission and named it after a bright indigo line in its spectrum.
In more detail
Indium sits in group 13 of the periodic table. It shares many chemical traits with its vertical neighbors, gallium and thallium. Indium typically forms chemical compounds using a +3 oxidation state.
It can also use a +1 oxidation state in some cases. This lower state becomes more stable in heavier group 13 elements. Chemists call this trend the inert pair effect, where outer electrons resist chemical reactions.
Indium does not react noticeably with regular room-temperature water. However, the metal rapidly dissolves when placed in strong mineral acids. It maintains a shiny, silvery surface well over time.
This happens because it does not easily oxidize or tarnish in normal atmospheric air. A defining physical trait of indium is its extreme softness and strange mechanical behavior. If you manually bend a bar of pure solid indium, it emits a high-pitched crackling sound.
Chemists refer to this noise as the indium cry. This sound occurs due to internal crystal twinning, where microscopic crystals shift and rub against each other. Indium rarely occurs as an independent mineral deposit in the Earth's crust.
Instead, companies extract it primarily as a trace byproduct. This extraction happens during the commercial processing and smelting of zinc and lead sulfide ores.
Key facts
| Field | General Chemistry |
|---|---|
| Symbol | In |
| Atomic number | 49 |
| Atomic mass | 114.82 u |
| Category | Post-Transition-Metal |
| State at room temperature | Solid |
| Melting point | 156.6 °C |
| Boiling point | 2072 °C |
| Year discovered | 1863 |
Manufacturers extensively use indium to create a special material called indium tin oxide, or ITO. This unique chemical compound acts as a transparent coating that easily conducts electricity. ITO is absolutely essential for building modern electronic devices. You will find it in smartphone touchscreens, liquid crystal displays, and advanced solar cells.
Frequently asked questions
Is indium metal safe to handle?
Solid indium metal is generally safe to handle and has low toxicity. However, you should treat its chemical compounds and fine dust with caution.
What exactly is the indium cry?
The indium cry is a crackling sound made when you bend solid indium. It is caused by internal microscopic crystals rubbing together.
Related terms
Sources & references
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