Indium (In)

Soft, silvery metal

Indium is a soft metal that squeaks when bent, used in every smartphone touchscreen, and with [Kr] 4d¹⁰ 5s² 5p¹, indium tin oxide (ITO) is transparent and electrically conductive, making it the standard material for touchscreens and LCD displays. Indium solder makes the tinny sound when rubbed.

Key metrics

Density7.31g/cm³

Melting point430K

Boiling point2,345K

Electronegativity1.78Pauling

Discovery

1863discovered

Discovered by: Ferdinand Reich
Reactivity profile: Soft and malleable
Reactivity: Low
Bonding: Metallic

Electron configuration

\textcolor{#6b7280}{[Kr]}\; \textcolor{#22c55e}{4_{d}^{10}}\; \textcolor{#ef4444}{5_{s}^{2}}\; \textcolor{#3b82f6}{5_{p}^{1}}

[Kr] 4d10 5s2 5p1

Wave function

\Psi_{\text{In}} \approx \frac{1}{\sqrt{49!}} \det \left| \chi_1(\mathbf{r}_1) \dots \chi_{49}(\mathbf{r}_{49}) \right|

Probability density $|\Psi|^2$ across the In valence shell.

Crystal structure

Tetragonal

Lattice constantsa 1.00 · b 1.00 · c 1.20

Cell anglesα = β = γ = 90°

Coordination number—

Atoms per cell—

Atomic packing factor0.64

Physical properties

Atomic radius: 156 pm
Ionization energy: 558 kJ/mol
Electron affinity: 29 kJ/mol
Crystal structure: Tetragonal

Oxidation states

+1+3

Acid/base

Can act as acid or base

Strongly acidicStrongly basic

State at 25 °CSolid

430 K2345 K298 K

Emission spectrum

3 transitions

380450500550600650700780

VioletBlueGreenYellowRed

410.2nmIn I (violet)Violet70%

425.7nmIn IViolet50%

451.1nmIn I (blue)Blue100%

Dominant line 451.1 nmRange 410–451 nmTransitions 3