Indium
Definition and meaning of Indium in chemistry.
Indium is a very soft, silvery-white metal represented by the chemical symbol In and an atomic number of 49. It is a relatively rare post-transition metal that is exceptionally malleable, allowing it to be easily deformed and physically cut with a simple knife. The element was discovered in 1863 through spectroscopic analysis and named for the vivid indigo blue line in its emission spectrum.
In more detail
Positioned in group 13 of the periodic table, indium belongs to the post-transition metals and shares distinct chemical similarities with its vertical neighbors, gallium and thallium. It typically forms chemical compounds in the +3 oxidation state, although the +1 oxidation state also exists and gradually becomes more stable in heavier group elements due to the inert pair effect. Indium does not react perceptibly with ambient water but rapidly dissolves in strong mineral acids, and it maintains its shiny surface well since it does not easily oxidize in standard atmospheric air. A defining, peculiar physical characteristic is its extreme softness and distinct mechanical behavior; a bar of pure solid indium emits a high-pitched crackling sound, known as the indium cry, when manually bent due to internal crystal twinning. The element rarely occurs as an independent mineral deposit, being extracted primarily as a trace commercial byproduct during the 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 |
Indium is extensively utilized to manufacture indium tin oxide (ITO), a transparent conductive coating that is absolutely essential for modern touchscreens, liquid crystal displays, and solar cells.
Frequently asked questions
Is indium metal safe to handle?
Solid indium metal is generally considered safe to handle and possesses low toxicity, although its chemical compounds and fine dust should be treated with appropriate caution.
What exactly is the indium cry?
The indium cry is an audible crackling sound produced when a piece of solid indium is bent, which is caused by the friction of its internal microscopic crystals twinning.