Element 49 · Post-transition metal
Indium (In) — Element 49
Indigo spectral line
Indium (In) is a post-transition metal in Period 5, Group 13 of the periodic table with atomic number 49, standard atomic weight 114.82 u, and ground-state electron configuration [Kr] 4d¹⁰ 5s² 5p¹. At standard temperature and pressure it is classified as a solid with 3 valence electrons and common oxidation states +3.
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What are the atomic properties and physical constants of Indium?
Reference constants compiled from IUPAC standard atomic weights, the NIST Atomic Spectra Database, and the CRC Handbook.
- Atomic number (Z)
- 49
- Standard atomic mass
- 114.82 u
- Chemical family
- Post-transition metal
- Ground-state configuration
- [Kr] 4d¹⁰ 5s² 5p¹
- Electrons per shell
- 2, 8, 18, 18, 3
- Valence electrons
- 3
- Common ion charges / oxidation states
- +3
- Phase at STP
- Solid
- Pauling electronegativity
- 1.78 Pauling
- First ionization energy
- 558 kJ/mol
- Atomic radius
- 156 pm
- Melting point
- 157 °C
- Boiling point
- 2,072 °C
- Discovery year
- 1863
- Table coordinate
- Period 5, Group 13
- Radioactivity
- Has stable isotope(s)
How are electrons arranged across Indium’s shells?
A neutral Indium atom contains 49 electrons distributed across 5 occupied principal energy shells ([Kr] 4d¹⁰ 5s² 5p¹). The table below compares Indium’s shell occupancy against each shell’s theoretical 2n² capacity.
| Principal Shell (n) | Spectroscopic Letter | Electrons in In | Max Shell Capacity (2n²) |
|---|---|---|---|
| n = 1 | K | 2 e⁻ | 2 e⁻ |
| n = 2 | L | 8 e⁻ | 8 e⁻ |
| n = 3 | M | 18 e⁻ | 18 e⁻ |
| n = 4 | N | 18 e⁻ | 32 e⁻ |
| n = 5 | O | 3 e⁻ | 50 e⁻ |
Frequently Asked Questions about Indium (In)
What is the atomic mass and atomic number of Indium (In)?
Indium (In) has atomic number Z = 49 (49 protons in its nucleus) and an IUPAC standard atomic weight of 114.82 u. It sits in Period 5, Group 13 and is classified as a post-transition metal.
What is the ground-state electron configuration of Indium?
The neutral ground-state electron configuration of Indium (Z = 49) is [Kr] 4d¹⁰ 5s² 5p¹. Across its 5 occupied principal shells (n = 1 to n = 5), the electrons per shell are 2, 8, 18, 18, 3, with 3 valence electrons participating in bonding.
What are the common ion charges and electronegativity of Indium?
Indium commonly forms +3 oxidation states or ion charges in compounds. Its Pauling electronegativity is 1.78 and its first ionization energy is 558 kJ/mol.
When was Indium discovered and what is it used for?
Indium was discovered in 1863 (Indigo spectral line). Touchscreens (ITO), solders
How does Indium compare to neighboring elements?
Other post-transition metal elements: