Indium helps make a useful combination possible: a coating that conducts electricity while remaining transparent. Indium tin oxide is used in screens and solar cells. Other indium compounds are semiconductors, connecting this soft metal to materials that control electrical signals and interact with light.
FROM ELEMENT TO APPLICATION
AN ELEMENT IN CONTEXT
How can a display layer conduct charge while still passing visible light?
Indium tin oxide thin film
FOLLOW THIS RELATIONSHIP
Form a conducting oxide film
Indium tin oxide is prepared as a thin film. Its useful properties belong to the oxide material rather than to bulk indium metal.
Explore the model (optional)
InFORM → INTERACTION → CONSEQUENCE
Follow the explanation in either direction. These are authored steps, not a physical clock.
Optional: check your understanding
USE THE EXPLANATION
Which evidence best evaluates whether a film can serve this role?
Atomic identity, reference properties and structure models
INTERACTIVE 3D49 visible sites
An electron censusDrag to rotate · scroll or pinch to zoom
[Kr] 4d10 5s2 5p1. Grouping electrons by principal shell connects the neutral-atom configuration to periodic-table patterns.
What this representation means
A three-dimensional counting diagram. Dots are count markers, not measured electron positions; spherical placement and spacing are arbitrary. There are no electron trajectories here. Orbitals describe quantum states.
Ferdinand Reich and Hieronymus Theodor Richter identified indium in 1863 while examining zinc-bearing material. A distinctive indigo line provided the clue and the name; chemical separation then established the new material. This is a strong example of spectroscopy extending discovery beyond visible appearance: a small constituent can leave a recognizable optical signal even when it does not form an obvious separate specimen.
1863
Indigo line observed
Reich and Richter found an unfamiliar spectral signal.
1863
New element announced
Chemical investigation supported the identification of indium.
Indium is dispersed in zinc-bearing minerals and is mainly recovered from residues generated during zinc-ore processing. This makes choices part of its availability. A resource may contain indium without producing it as a saleable material, because occurrence and economical recovery are different questions.
Pure indium is a soft metal, while indium-containing compounds can be semiconducting or transparently conducting. Indium phosphide and indium tin therefore belong to different materials stories. Their useful electronic behavior depends on bonding, composition, and structure, not simply on the appearance or softness of a metal sample.
Each section links its supporting references. Descriptions and diagrams were authored for this atlas. Source checks completed. Source checks dated 2026-09-06.
CITE THIS PAGE
Family labels and the group-3 layout are teaching conventions. A table position does not establish an unknown bulk property. Electronic configurations refer to neutral atoms; ions and material environments require their own account.
Read each reference property together with its units, conditions and the reference information below.
Not yet recorded: electron affinity, second ionization energy, ground-state term symbol, van der waals radius, thermal conductivity, specific heat capacity, electrical resistivity, crystal structure, lattice parameter a, space group, abundance in seawater, abundance in the universe, annual production, supply-risk listing, hazard classification, biological role, cas registry number, pubchem cid, wikidata item. These families are declared and awaiting an ingestion run against the source each names; they are listed here rather than shown as empty rows.
Physical
Intended reference: CRC Handbook of Chemistry and Physics · CRC Press
Phase at 20 °C
solid
293.15 K, 101.325 kPa
Melting point in K
429.75 K
at standard pressure unless noted
Boiling point in K
2345 K
101.325 kPa
Density in g/cm³
7.31 g/cm³
solids and liquids at 293 K; gases at 273 K and 101.325 kPa
Atomic and electronic
Intended reference: Pauling electronegativity scale · Widely tabulated; original in The Nature of the Chemical Bond
Electronegativity in Pauling
1.78 Pauling
Pauling scale
First ionization energy in kJ/mol
558.3 kJ/mol
gas-phase neutral atom, ground state
Covalent radius in pm
142 pm
single-bond covalent radius
Common oxidation states
+3
states met in ordinary compounds; not exhaustive
Occurrence and identity
Intended reference: CRC Handbook of Chemistry and Physics · CRC Press
Abundance in the crust in mg/kg
0.25 mg/kg
upper continental crust, mass fraction
Has stable isotopes
Yesderived
Discovery year in CE
1863 CEderived
WHERE IT SITS AMONG ITS NEIGHBORS
Electronegativity across period 5
In 1.78 Pauling · Indium
Electronegativity across period 5. Exact values.
Rb
0.82
Sr
0.95
Y
1.22
Zr
1.33
Nb
1.6
Mo
2.16
Tc
1.9
Ru
2.2
Rh
2.28
Pd
2.2
Ag
1.93
Cd
1.69
In
1.78
Sn
1.96
Sb
2.05
Te
2.1
I
2.66
Xe
2.6
Electronegativity down group 13
In 1.78 Pauling · Indium
Electronegativity down group 13. Exact values.
B
2.04
Al
1.61
Ga
1.81
In
1.78
Tl
1.62
The trend uses the same reference-property values as the periodic table. Elements with no recorded value are left out of the line rather than drawn at zero.
