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Indium (In)

Indium is a chemical element of the periodic table with chemical symbol In and atomic number 49 with an atomic weight of 114.818 u and is classed as post-transition metal and is part of group 13 (boron group). Indium is solid at room temperature.

Indium in the periodic table

Atomic number49
Group13 (Boron group)
ClassificationPost-Transition Metal
AppearanceSilvery lustrous gray
Color Silver
Number of protons49 p+
Number of neutrons66 n0
Number of electrons49 e-
From Wikipedia, the free encyclopediaIndium is a chemical element with symbol In and atomic number 49. It is a post-transition metallic element that is rare in Earth's crust. The metal is very soft, malleable and easily fusible, with a melting point higher than sodium, but lower than lithium or tin.

Physical properties

Phase at STPSolid
Density7.31 g/cm3
Atomic weight114.818 u

Thermal properties

Melting point429.749 K
156.599 °C
313.8782 °F
Boiling point2345 K
2071.85 °C
3761.33 °F
Heat of vaporization226.35 kJ/mol

Atomic properties

Electronegativity (Pauling Scale)1.78
Electron affinity37.043 kJ/mol
Oxidation states−5, −2, −1, +1, +2, +3
(an amphoteric oxide)
Ionization energies
  1. 558.3 kJ/mol
  2. 1820.7 kJ/mol
  3. 2704 kJ/mol
  4. 5210 kJ/mol

Electron configuration for indium

Electron configuration
Shorthand configuration
[Kr] 4d10 5s2 5p1
Electron configuration
Full configuration
1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 5s2 5p1
Electron configuration chart
Electrons per shell2, 8, 18, 18, 3
Valence electrons 3
Valency electrons 3
Bohr model
IndiumElectron shell for Indium, created by Injosoft ABIn
Figure: Shell diagram of Indium (In) atom.
Orbital Diagram

The history of Indium

DiscoveryFerdinand Reich, Hieronymous Theodor Richter (1863)
First isolationHieronymous Theodor Richter (1864)
Discovery of indium
In 1863, the German chemists Ferdinand Reich and Hieronymous Theodor Richter were testing ores from the mines around Freiberg, Saxony. They dissolved the minerals pyrite, arsenopyrite, galena and sphalerite in hydrochloric acid and distilled raw zinc chloride. Reich, who was color-blind, employed Richter as an assistant for detecting the colored spectral lines. Knowing that ores from that region sometimes contain thallium, they searched for the green thallium emission spectrum lines. Instead, they found a bright blue line. Because that blue line did not match any known element, they hypothesized a new element was present in the minerals. They named the element indium, from the indigo color seen in its spectrum, after the Latin indicum, meaning 'of India'. Richter went on to isolate the metal in 1864. An ingot of 0.5 kg (1.1 lb) was presented at the World Fair 1867. Reich and Richter later fell out when the latter claimed to be the sole discoverer.


List of unique identifiers for Indium in various chemical registry databases
CAS Number7440-74-6
ChemSpider ID4514408
EC number231-180-0
PubChem CID Number5359967