Element 77 · Transition metal
Iridium (Ir) — Element 77
Greek iris — rainbow
Iridium (Ir) is a transition metal in Period 6, Group 9 of the periodic table with atomic number 77, standard atomic weight 192.22 u, and ground-state electron configuration [Xe] 4f¹⁴ 5d⁷ 6s². At standard temperature and pressure it is classified as a solid with 9 valence electrons and common oxidation states +3, +4.
Spark plugs, crucibles, jewelry
What are the atomic properties and physical constants of Iridium?
Reference constants compiled from IUPAC standard atomic weights, the NIST Atomic Spectra Database, and the CRC Handbook.
- Atomic number (Z)
- 77
- Standard atomic mass
- 192.22 u
- Chemical family
- Transition metal
- Ground-state configuration
- [Xe] 4f¹⁴ 5d⁷ 6s²
- Electrons per shell
- 2, 8, 18, 32, 15, 2
- Valence electrons
- 9
- Common ion charges / oxidation states
- +3, +4
- Phase at STP
- Solid
- Pauling electronegativity
- 2.20 Pauling
- First ionization energy
- 880 kJ/mol
- Atomic radius
- 180 pm
- Melting point
- 2,446 °C
- Boiling point
- 4,428 °C
- Discovery year
- 1803
- Table coordinate
- Period 6, Group 9
- Radioactivity
- Has stable isotope(s)
How are electrons arranged across Iridium’s shells?
A neutral Iridium atom contains 77 electrons distributed across 6 occupied principal energy shells ([Xe] 4f¹⁴ 5d⁷ 6s²). The table below compares Iridium’s shell occupancy against each shell’s theoretical 2n² capacity.
| Principal Shell (n) | Spectroscopic Letter | Electrons in Ir | 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 | 32 e⁻ | 32 e⁻ |
| n = 5 | O | 15 e⁻ | 50 e⁻ |
| n = 6 | P | 2 e⁻ | 72 e⁻ |
Frequently Asked Questions about Iridium (Ir)
What is the atomic mass and atomic number of Iridium (Ir)?
Iridium (Ir) has atomic number Z = 77 (77 protons in its nucleus) and an IUPAC standard atomic weight of 192.22 u. It sits in Period 6, Group 9 and is classified as a transition metal.
What is the ground-state electron configuration of Iridium?
The neutral ground-state electron configuration of Iridium (Z = 77) is [Xe] 4f¹⁴ 5d⁷ 6s². Across its 6 occupied principal shells (n = 1 to n = 6), the electrons per shell are 2, 8, 18, 32, 15, 2, with 9 valence electrons participating in bonding.
What are the common ion charges and electronegativity of Iridium?
Iridium commonly forms +3, +4 oxidation states or ion charges in compounds. Its Pauling electronegativity is 2.20 and its first ionization energy is 880 kJ/mol.
When was Iridium discovered and what is it used for?
Iridium was discovered in 1803 (Greek iris — rainbow). Spark plugs, crucibles, jewelry
How does Iridium compare to neighboring elements?
Other transition metal elements: