Indium (In)
Element 49 · Post-transition metal · Solid at 25 °C · Group 13, Period 5
Indium tin oxide is the transparent conductor behind touchscreens; indium metal is soft enough to leave a mark on paper.
On the periodic table, indium sits in group 13 — the boron group — in period 5. It is one of 12 elements classified as a post-transition metal, and at room temperature (25 °C) it is a solid.
The post-transition metals sit between the transition metals and the metalloids. They are genuine metals — shiny and conductive — but softer, weaker, and lower-melting than the d-block metals, and their chemistry has more covalent character. Everyday examples from this family include aluminium foil, tin cans, and lead batteries.
Properties of indium
| Atomic number (Z) | 49 |
|---|---|
| Symbol | In |
| Atomic mass | 114.82 |
| Category | Post-transition metal |
| Group | 13 |
| Period | 5 |
| Block | p-block |
| Metal / nonmetal | Metal |
| State at 25 °C | Solid |
| Electron configuration | [Kr] 4d10 5s2 5p1 |
| Electronegativity (Pauling) | 1.78 |
| Melting point | 156.6 °C (429.75 K / 313.88 °F) |
| Boiling point | 2,072 °C (2,345.15 K / 3,761.6 °F) |
| Density | 7.31 g/cm³ |
Position in the periodic table
Indium shares group 13 — the boron group with Boron (B), Aluminium (Al), Gallium (Ga), Thallium (Tl), Nihonium (Nh). Elements in the same group have the same number of outer electrons, so they tend to behave alike chemically — comparing them is one of the fastest ways to see periodic trends in action.
Physical properties
Indium melts at 156.6 °C (429.75 K / 313.88 °F) and boils at 2,072 °C (2,345.15 K / 3,761.6 °F), giving it a liquid range of about 1,915.4 °C at standard pressure.
Its density is 7.31 g/cm³.
See also: the interactive periodic table, how to read the periodic table, metals, nonmetals & metalloids.