Atomic / phase data
Reference values are evaluated.
Tetragonal metal
Ordinary indium bulk structure is tetragonal; viewer is schematic.
ITO / compound distinction
Transparent-conductor behavior of ITO is not assigned to pure indium metal.
115In radioactivity
Dominant natural 115In is radioactive with an extraordinarily long half-life.
Supply geography
By-product supply context is dated/selective.
The lens describes evidence status, not confidence theatre. “Unknown” is kept unknown, and teaching schematics are not presented as direct measurements.
Indium (In)
Indium is element 49, a soft post-transition metal whose low melting point and transparent-conductor compounds connect periodic chemistry to touchscreens, displays and specialty semiconductors.
Indium atomic number, mass, electron configuration and key properties
Indium: quick answers
How many protons, neutrons and electrons does indium have?
Indium’s atomic number is 49, so every indium atom has 49 protons, and a neutral atom also has 49 electrons. Its most common natural isotope, indium-115, has 66 neutrons (other isotopes have different neutron counts).
What is the symbol for indium?
The chemical symbol for indium is In.
Is indium a solid, liquid or gas at room temperature?
Indium is a solid at room temperature (about 25 °C).
What family (group) is indium in?
Indium is a post-transition metal, in group 13, period 5 of the periodic table.
How many valence electrons does indium have?
Indium has 3 valence electrons, the electrons in its outer shell, which matches its position in group 13.
What is the electron configuration of indium?
The ground-state electron configuration of indium is [Kr] 4d¹⁰ 5s² 5p¹.
From atomic number to chemistry
Read these as a chain of causes, not as isolated facts. Each step links to the concept hub if you want the underlying idea explained.
49 protons define indium.
The reference ground-state configuration frames atomic and chemical behavior.
Periodic position organizes recurring trends without replacing element-specific evidence.
The teaching nucleus is one isotope, not the relative atomic mass.
Phase claims preserve measured/evaluated/predicted/unknown evidence labels.
Indium in its period and family
Indium sits below gallium in Group 13. Its 5s²5p¹ outer pattern supports +3 chemistry, while heavier-atom effects make +1 chemistry more important than in aluminium.
Indium Visual Lab
Explore In across the teaching nucleus, isolated-atom orbitals, evidence-aware material structure and temperature/evidence views, then connect those models to uses, isotopes and source-backed context.
Every mark points to one exact feature
The numbered markers explain the same information system used throughout Element Lookup. Unknown or predicted fields remain visibly labelled rather than being replaced with guesses.
Indium in one minute
Atomic number 49 means 49 protons.
Neutral indium has [Kr] 4d¹⁰ 5s² 5p¹.
Indium is a soft post-transition metal with a 429.75 K melting point.
ITO is a compound material, not elemental indium.
Natural indium is mostly very long-lived radioactive ¹¹⁵In, alongside stable ¹¹³In.
Shell rings organize electron counts. They are not electron trajectories or orbital shapes.
2 · 8 · 18 · 18 · 3 electrons
5s and 5p clouds are isolated-atom probability models. They do not depict electron bands in indium metal or indium-containing semiconductors.
Ordinary indium is tetragonal. The viewer uses a body-centred tetragonal teaching cell to show anisotropic cell proportions without claiming a crystallographic coordinate reconstruction.. The viewer is evidence-aware: measured structures are identified as such; unknown bulk structures stay unknown.
Teaching visualization; not a literal finite sample or thermal trajectory.What this model does—and does not—show
5s and 5p clouds are isolated-atom probability models. They do not depict electron bands in indium metal or indium-containing semiconductors.
Where do I meet indium?
Clickable learning cards connect the element to materials, environment, technology, biology or research - depending on what the evidence actually supports.
Transparent conductors
Indium tin oxide is widely used where electrical conductivity and optical transparency are both needed.
Soft tetragonal metal → transparent conductors → isotope nuance
Indium links a simple Group 13 outer pattern to unusually soft bulk metal, by-product supply and compound materials that can conduct while remaining optically transparent.
Tetragonal In
Ordinary indium is a soft tetragonal post-transition metal.
Gallium, indium and thallium
The ns²np¹ pattern repeats while inert-pair effects and bulk structure change down Group 13.
| Valence | 4s²4p¹ |
|---|---|
| Melt | 302.9 K |
| Valence | 5s²5p¹ |
|---|---|
| Melt | 429.75 K |
| Valence | 6s²6p¹ |
|---|---|
| Context | +1 increasingly important |
Indium properties: atomic, physical, thermal and chemical
Categories follow the science of this element rather than a fixed decorative template. Each row carries condition/provenance context and an evidence label; unknown values stay unknown.
| Property | Value | Context / provenance | Evidence |
|---|---|---|---|
| Atomic number | 49 | Source-reviewed; see Sources below | Evaluated |
| Relative atomic mass | 114.818 | Source-reviewed; see Sources below | Evaluated |
| Ground-state electron configuration | [Kr] 4d¹⁰ 5s² 5p¹ | Source-reviewed; see Sources below | Evaluated |
| Group / period / block | Group 13 · Period 5 · p-block | Periodic-table placement | Evaluated |
| Electronegativity | 1.78 | Source-reviewed; see Sources below | Evaluated |
| Reference isotope | ¹¹⁵In | Source-reviewed; see Sources below | Evaluated |
| Property | Value | Context / provenance | Evidence |
|---|---|---|---|
| State context | Soft silvery metal | Source-reviewed; see Sources below | Evaluated |
| Density | 7.31 g/cm³ | Source-reviewed; see Sources below | Evaluated |
| Material / molecular structure | Body-centred tetragonal | Ordinary indium is tetragonal. The viewer uses a body-centred tetragonal teaching cell to show anisotropic cell proportions without claiming a crystallographic coordinate reconstruction. | Measured |
| Classification | Post-transition metal | Periodic-table / chemistry classification | Evaluated |
| Structure-model scope | Ordinary indium is tetragonal. The viewer uses a body-centred tetragonal teaching cell to show anisotropic cell proportions without claiming a crystallographic coordinate reconstruction. | Teaching visualization; exact crystallographic coordinates are not implied unless stated. | Reviewed |
| Property | Value | Context / provenance | Evidence |
|---|---|---|---|
| Melting / transition reference | 429.75 K | Source-reviewed; see Sources below | Evaluated |
| Boiling / gas reference | 2300 K | Source-reviewed; see Sources below | Evaluated |
| Phase-path context | At approximately standard pressure, indium is solid below 429.75 K, liquid to about 2300 K, and gaseous above the boiling reference. | Shared phase registry drives the slider, regions and markers. | Evaluated |
| Condition warning | Temperature and pressure define phase behavior; purity/allotropy may matter. | Teaching condition statement | Reviewed |
| Property | Value | Context / provenance | Evidence |
|---|---|---|---|
| Ordinary electrical behavior | Metallic conductor | Qualitative bulk behavior; exact resistivity depends on temperature, purity and alloy state. | Measured |
| Conduction model | Collective solid-state electrons | Do not interpret isolated-atom orbital clouds as literal current paths. | Reviewed |
| Surface / compound caveat | Oxides, salts and alloys can behave differently from the pure metal | Material context | Reviewed |
| Engineering values | Condition-dependent | Use condition-specific materials data for engineering calculations. | Reviewed |
| Property | Value | Context / provenance | Evidence |
|---|---|---|---|
| Common oxidation states | +3, +1 | Source-reviewed; see Sources below | Evaluated |
| Ion / common ion context | In³⁺ | Source-reviewed; see Sources below | Evaluated |
| Periodic chemistry context | Indium sits below gallium in Group 13. Its 5s²5p¹ outer pattern supports +3 chemistry, while heavier-atom effects make +1 chemistry more important than in aluminium. | Element-specific interpretation | Reviewed |
| Chemistry caution | Elemental form, ions and compounds are distinct chemical objects. | Interpretive teaching rule | Reviewed |
| Property | Value | Context / provenance | Evidence |
|---|---|---|---|
| ¹¹³In | Stable natural isotope | Minor natural isotope. | Evaluated |
| ¹¹⁵In | Very long-lived radioactive natural isotope | Dominant natural isotope; its decay is so slow that ordinary samples are effectively persistent on human timescales. | Evaluated |
| Natural indium | Two-isotope mixture | Relative atomic mass reflects the terrestrial isotope mixture. | Evaluated |
| Teaching nucleus | ¹¹⁵In · 49 protons + 66 neutrons | Reference isotope used in the nucleus model | Reviewed |
Is Indium a solid, liquid or gas? State at temperature
At approximately standard pressure, indium is solid below 429.75 K, liquid to about 2300 K, and gaseous above the boiling reference.
Where on Earth is Indium found or produced?
Who discovered Indium, and when?
Ferdinand Reich and Hieronymous Richter identified indium spectroscopically by its indigo-blue line.
Richter isolated metallic indium.
Indium compounds and transparent conductive oxides became technologically important.
Electronics demand is closely tied to by-product recovery and recycling.
From by-product recovery to indium materials: high-level supply path
Indium is commonly recovered from residues and process streams generated while producing other metals, especially zinc.
Refining produces high-purity indium metal or chemical feedstocks.
Manufacturing converts those feedstocks into distinct compounds and coatings such as ITO or indium phosphide.
Recovery from manufacturing scrap and end-of-life products can supplement primary supply.
What is indium used for?
Displays & touch surfaces
ITO provides a transparent conductive layer in many display and interface technologies.
Semiconductors
InP, InGaN and related compounds support optoelectronic and electronic devices.
Low-melting alloys
Indium can lower melting temperatures and improve wetting in specialty alloys.
Research
Indium isotopes and compounds support spectroscopy, nuclear and materials research.
Indium isotopes and natural abundance
¹¹³In
Stable natural isotopeMinor natural isotope.
¹¹⁵In
Very long-lived radioactive natural isotopeDominant natural isotope; its decay is so slow that ordinary samples are effectively persistent on human timescales.
Natural indium
Two-isotope mixtureRelative atomic mass reflects the terrestrial isotope mixture.
Five-question Indium check
What is indium’s atomic number?
What is its simple outer pattern?
Which material is distinct from indium metal?
What is the ordinary crystal teaching model?
Which isotope nuance is important?
Indium questions students commonly ask
Each answer starts with the direct fact, then explains the chemistry, evidence or material context so the result is understandable rather than merely memorized.
What is indium?
Short answer: Indium is chemical element 49, a soft post-transition metal in Group 13.
Atomic number 49 means every indium nucleus contains 49 protons. In the periodic table, Indium is classified here as a post-transition metal in Period 5 and Group 13. Indium sits below gallium in Group 13. Its 5s²5p¹ outer pattern supports +3 chemistry, while heavier-atom effects make +1 chemistry more important than in aluminium.
Key point: In is element 49; its periodic position and electron structure explain the rest of the page.
Is indium a metal?
Short answer: Yes. It is generally classified as a post-transition metal.
This guide classifies Indium as a post-transition metal. Its periodic position is Period 5, p-block, Group 13. Indium sits below gallium in Group 13. Its 5s²5p¹ outer pattern supports +3 chemistry, while heavier-atom effects make +1 chemistry more important than in aluminium.
Key point: Periodic-table classification describes recurring atomic/chemical behavior; it does not make every element in a column physically identical.
What is the symbol for indium?
Short answer: In.
The symbol In is the standardized chemical abbreviation for element 49. In a chemical formula, In identifies indium atoms; a compound containing In is not automatically the same material as elemental indium.
Key point: In always identifies element 49.
What is indium used for?
Short answer: A major use is in indium-containing transparent conductive oxides; indium compounds are also used in semiconductors and specialty alloys.
Displays & touch surfaces: ITO provides a transparent conductive layer in many display and interface technologies. Semiconductors: InP, InGaN and related compounds support optoelectronic and electronic devices. Indium metal is not the same material as indium tin oxide (ITO). The element provides the In atoms, while ITO is a distinct oxide material whose electrical and optical behavior comes from a compound solid.
Key point: Always distinguish the pure element from the compound, alloy, isotope or device material that actually performs the application.
What is indium’s melting point?
Short answer: About 429.75 K, or 156.6 °C.
At approximately standard pressure, indium is solid below 429.75 K, liquid to about 2300 K, and gaseous above the boiling reference.
Key point: Phase statements need temperature, pressure and evidence context.
What is indium’s electron configuration?
Short answer: [Kr] 4d¹⁰ 5s² 5p¹.
The neutral-atom ground-state reference used on this page is [Kr] 4d¹⁰ 5s² 5p¹. This is an isolated-atom reference: bonding and ion formation can change which outer electrons are present or chemically active. The listed common oxidation-state context is +3, +1, which helps connect the atomic configuration to ordinary chemistry without treating electron counting as a single universal rule.
Key point: Electron configuration is a ground-state atomic reference, not a literal picture of every compound.
Is indium radioactive?
Short answer: Natural indium contains stable ¹¹³In and dominant ¹¹⁵In, which is radioactive but has an extraordinarily long half-life.
¹¹³In: Stable natural isotope: Minor natural isotope. ¹¹⁵In: Very long-lived radioactive natural isotope: Dominant natural isotope; its decay is so slow that ordinary samples are effectively persistent on human timescales.
Key point: Radioactivity is isotope-specific; do not apply one isotope’s nuclear behavior to every atom of the element.
Scientific sources for Indium
- Royal Society of Chemistry - Indium
- NIST - Atomic Data / Indium
- USGS - Mineral Commodity Summaries 2026
Questions to ask next about Indium
A good element lesson should lead to the next useful question, not end after a list of facts.
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