Indium (In)
Indium is element 49, a post-transition metal in group 13, period 5. A neutral atom has 49 protons, 66 neutrons and 49 electrons, 3 of them valence electrons.
Post-transition metal- Atomic number
- 49
- Atomic mass
- 114.82 u
- Valence electrons
- 3
- Protons · neutrons
- 49 · 66
- Electrons per shell
- 2, 8, 18, 18, 3
- At room temperature
- solid
Bohr model of indium
The Bohr model draws indium as a nucleus of 49 protons and 66 neutrons, with its 49 electrons on 5 circular shells: 2 in shell 1, 8 in shell 2, 18 in shell 3, 18 in shell 4, 3 in shell 5. Press Build the atom to watch the shells fill from the inside out. The outer ring (the O shell) is dashed: the electrons there are the ones that take part in chemistry.
Real electrons don't travel in neat circles. They live in fuzzy orbitals, shown below, but the Bohr picture is the quickest way to count shells and valence electrons.
Electron configuration of indium
1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p¹
Short form (noble gas notation): [Kr] 5s² 4d¹⁰ 5p¹. The [Kr] stands for the electrons of krypton, the noble gas before it.
How many valence electrons does indium have?
Indium has 3 valence electrons.
Indium is in group 13, and for groups 13–18 you subtract 10 from the group number: 13 − 10 = 3. It tends to lose them and form a +3 ion.
Protons, neutrons and electrons
| Protons | 49 | equal to the atomic number |
|---|---|---|
| Electrons | 49 | equal to the protons in a neutral atom |
| Neutrons | 66 | mass number 115 − 49 protons |
Atoms of the same element can have different numbers of neutrons (isotopes). The count above uses the rounded atomic mass, the way it's taught in class.
Indium properties
| Symbol | In |
|---|---|
| Category | Post-transition metal |
| Group · period · block | 13 · 5 · p |
| Atomic mass | 114.82 u |
| State at 25 °C | solid |
| Melting point | 429.8 K (157 °C, 314 °F) |
| Boiling point | 2,345 K (2,070 °C, 3,760 °F) |
| Density | 7.31 g/cm³ |
| Electronegativity (Pauling) | 1.78 |
| Atomic radius | 193 pm |
| First ionization energy | 5.786 eV |
| Electron affinity | 0.3 eV |
| Oxidation states | +3 |
| Common ion charge | +3 |
| Discovered | 1863 by Ferdinand Reich |
Where indium sits on the periodic table
Group 13: Boron, Aluminum, Gallium, Thallium, Nihonium.
Questions about indium
How many valence electrons does indium have?
Indium has 3 valence electrons.
How many protons, neutrons and electrons does indium have?
A neutral indium atom has 49 protons and 49 electrons. Its most common form has about 66 neutrons (mass number 115 − 49 protons).
What is the electron configuration of indium?
1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p¹, written in short form as [Kr] 5s² 4d¹⁰ 5p¹.
What does the Bohr model of indium look like?
A nucleus of 49 protons and 66 neutrons, circled by 5 electron shells holding 2, 8, 18, 18, 3 electrons.
What is the atomic number of indium?
49. The atomic number is the number of protons in the nucleus, and it is what makes an atom indium.