Ir Iridium

Quick answerIridium (Ir) is a transition metal with atomic number 77 and an atomic mass of 192.22 (2023), in group 9, period 6. It was discovered by Smithson Tennant in 1803. It is used for spark plugs and crucibles. Its electron configuration is [Xe] 4f14 5d7 6s2.

Iridium is the most corrosion-resistant metal known, and a thin layer of it in rocks marks the asteroid that killed the dinosaurs.

Key facts

Symbol	Ir
Atomic number	77
Atomic mass	192.22 (IUPAC standard atomic weight, 2023)
Category	transition metal
Group	9
Period	6
Block	d-block
Electron configuration	[Xe] 4f14 5d7 6s2
Discovered	Smithson Tennant, 1803
Uses	spark plugs, crucibles, electrical contacts, pen tips, catalysts

Quick quiz

Three questions from the facts on this page. No sign-up, no score is saved.

1. What is the chemical symbol of Iridium?

V Ti Sc Ir

2. What is the atomic number of Iridium?

77 76 79 78

3. Which category does Iridium belong to?

halogen alkali metal noble gas transition metal

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Keep exploring

• Periodic table — all 118 elements
• Hafnium (Hf) — another transition metal, atomic number 72
• Tantalum (Ta) — another transition metal, atomic number 73
• Tungsten (W) — another transition metal, atomic number 74
• Rhenium (Re) — another transition metal, atomic number 75
• Osmium (Os) — another transition metal, atomic number 76
• Platinum (Pt) — another transition metal, atomic number 78
• Gold (Au) — another transition metal, atomic number 79
• Mercury (Hg) — another transition metal, atomic number 80
• Rutherfordium (Rf) — another transition metal, atomic number 104
• Dubnium (Db) — another transition metal, atomic number 105
• All transition metal elements — on the periodic table

Sources & last updated

• CIAAW — Standard Atomic Weights
• PubChem Periodic Table
• Wikipedia — Timeline of chemical element discoveries

Last updated: 2026-11-12. Figures are shown with their year; where sources disagree, the value is left out rather than estimated.