Indium
post transition metalProperties
| Property | Value |
|---|---|
| Atomic Mass | 114.82 amu |
| Category | post transition metal |
| Group | 13 |
| Period | 5 |
| Electron Configuration | 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p1 |
| Electronegativity | 1.78 (Pauling) |
| Oxidation States | 3, 1 |
| Melting Point | 429.75 K (156.6 °C) |
| Boiling Point | 2345 K (2071.8 °C) |
| Density | 7.31 g/cm³ |
| Discovered By | Ferdinand Reich, Hieronymus Theodor Richter (1863) |
About Indium
Indium is one of the few metals soft enough to mark with a fingernail and ductile enough to cold-weld to itself, which is exactly why cryogenic vacuum people use thin In wires and washers as gaskets — they squeeze into every imperfection on a flange and seal at 4 K. Its low melting point (429.75 K, about 156 °C) and tendency to wet glass and ceramics also make it the basis for half the indium-bismuth-tin solders used to bond temperature-sensitive electronics. The high-volume use, though, is indium tin oxide. ITO is roughly 90% In₂O₃ doped with SnO₂, and the combination of >85% optical transmission with sheet resistances near 10 Ω/□ is what makes touchscreens possible. Indium itself is a byproduct of zinc smelting — there are no indium ores, just trace levels in sphalerite that get concentrated in flue dusts. World refined production is only around 900 tonnes a year.
Fun Fact
Bite a piece of indium and you'll hear a faint cry — the same crackling sound tin makes when it twins under deformation. The metal is soft enough to mark with a fingernail and ductile enough to cold-weld to itself, which is why cryogenic seal washers are still made out of it.
Common Uses
- Indium tin oxide (ITO) transparent electrodes on touchscreens and OLEDs
- Cold-weldable In gasket wire for cryogenic ultra-high-vacuum seals
- Low-temperature solder alloys (In-Bi-Sn) for sensitive electronics
- CIGS thin-film photovoltaic absorber layers
- InP and InSb wafers for IR detectors and high-frequency RF devices