What is Indium's atomic number?

Indium has atomic number 49, meaning it has 49 protons in its nucleus. Its chemical symbol is In.

What is Indium used for?

Indium's primary use is in indium tin oxide (ITO), a transparent electrical conductor coating used in LCD displays, touchscreens, and flat-panel TVs. It is also used in low-melting alloys, solders, and thin-film solar cells.

What is Indium's electron configuration?

Indium's full electron configuration is [Kr] 4d10 5s2 5p1. The single 5p electron drives the +3 oxidation state that dominates its chemistry.

Indium is considered a critical raw material. It is not abundant — crustal abundance is about 0.049 ppm — and is primarily recovered as a byproduct of zinc ore smelting.

Who discovered Indium?

Indium was discovered in 1863 by German chemists Ferdinand Reich and Hieronymus Theodor Richter using spectroscopy. The bright indigo spectral line gave the element its name.

Indium and its compounds are considered moderately toxic. Occupational exposure to indium compounds (especially indium phosphide) has been linked to lung disease. Elemental indium poses lower risk but should be handled with care.

Indium Element Properties

Explore the complete physical and chemical properties of Indium (In, element 49) — a soft post-transition metal essential in touchscreens and semiconductors.

114.818

Indium

Post-transition Metal · Period 5 · Group 13

Melting Point

156.6 °C

Boiling Point

2072 °C

Density

7.31 g/cm³

Atomic Mass

114.818 u

Electron Shell Configuration

[Kr] 4d¹⁰ 5s² 5p¹

Shells: 2, 8, 18, 18, 3

Filter Properties

Property	Value
Element Name	Indium
Symbol	In
Atomic Number	49
Atomic Mass	114.818 u
Category	Post-transition Metal
Group	13 (IIIA)
Period	5
Block	p-block
CAS Number	7440-74-6
Discovered	1863
Discovered By	Ferdinand Reich & Hieronymus T. Richter
Named After	Indigo spectral line (Latin: indicum)
Standard State	Solid at 25 °C
Appearance	Silvery-white, lustrous soft metal

Property	Value
Electron Configuration	[Kr] 4d10 5s2 5p1
Electrons Per Shell	2, 8, 18, 18, 3
Number of Protons	49
Number of Neutrons (In-115)	66
Number of Electrons	49
Valence Electrons	3
Oxidation States	+3 (primary), +1 (rare)
Electronegativity (Pauling)	1.78
Electron Affinity	28.9 kJ/mol
First Ionization Energy	558.3 kJ/mol
Second Ionization Energy	1820.7 kJ/mol
Third Ionization Energy	2704 kJ/mol
Atomic Radius (calc.)	156 pm
Covalent Radius	142 pm
Van der Waals Radius	193 pm
Stable Isotopes	In-113 (4.3%), In-115 (95.7%)

Property	Value
Melting Point	156.6 °C (313.9 °F / 429.75 K)
Boiling Point	2072 °C (3762 °F / 2345 K)
Density (solid, 25 °C)	7.31 g/cm³
Density (liquid, 156.6 °C)	7.02 g/cm³
Heat of Fusion	3.281 kJ/mol
Heat of Vaporization	231.8 kJ/mol
Specific Heat Capacity	0.233 J/(g·K)
Thermal Conductivity	81.8 W/(m·K)
Thermal Expansion	32.1 µm/(m·K) at 25 °C
Electrical Resistivity	83.7 nΩ·m at 20 °C
Young's Modulus	11 GPa
Brinell Hardness	8.83 MPa
Mohs Hardness	1.2
Crystal Structure	Face-centered tetragonal
Magnetic Ordering	Diamagnetic
Speed of Sound	1215 m/s (thin rod, 20 °C)

Property	Value
Reactivity	Low; stable in air at room temperature
Reaction with Water	No reaction at room temperature; reacts slowly with boiling water
Reaction with Air	Stable; thin In2O3 oxide layer forms at elevated temperatures
Reaction with Acids	Dissolves in dilute HCl and H2SO4; slower in HNO3
Reaction with Bases	Poorly amphoteric; slow dissolution in concentrated NaOH
Key Industrial Compound	Indium tin oxide (ITO) — transparent conductor for displays
Semiconductor Compound	Indium phosphide (InP) — high-speed electronics, solar cells
LED Compound	Indium gallium nitride (InGaN) — blue/green LEDs
Common Compounds	In2O3, InP, InAs, InSb, InCl3, In2S3
Oxidation State Range	+1, +2, +3 (+3 most stable)
Amphoteric Nature	Weakly amphoteric
Natural Occurrence	Trace in zinc, lead, and copper ores; 0.049 ppm crustal abundance
Global Production	~900 tonnes/year (mostly byproduct of zinc smelting)
Toxicity	Moderate; InP is a suspected carcinogen; handle with care

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Summary

Indium (In) is element 49 on the periodic table, a soft, silvery post-transition metal in group 13. It is best known for forming indium tin oxide (ITO), the transparent conductor used in virtually every touchscreen and LCD display. This reference tool presents all key physical, atomic, and chemical properties of Indium in one organized view.

How it works

All Indium property data is embedded directly in the page — no server call is needed.
Use the section tabs (Overview, Atomic, Physical, Chemical) to navigate different property groups.
Click any property row to copy its value to your clipboard.
The electron configuration diagram shows the shell distribution visually.
Use the search box to filter properties by name.

Use cases

Quick reference for students studying periodic table elements.
Verify Indium specs during semiconductor or display-panel research.
Teaching aid for explaining post-transition metal behavior.
Cross-check Indium isotope and thermodynamic data for lab work.
Explore Indium's role in ITO touchscreens and thin-film solar cells.
Support chemistry homework and exam preparation.

Frequently Asked Questions

Last updated: 2026-09-30 · Reviewed by Nham Vu