77
Ir
Iridium
193
Iridium (Ir)
Transition MetalGroup 9Period 6d-block-block
Iridium is a chemical element with symbol Ir and atomic number 77. A very hard, brittle, silvery-white transition metal of the platinum group, iridium is generally credited with being the second densest element (after osmium) based on measured density, although calculations involving the space lattices of the elements show that iridium is denser. It is also the most corrosion-resistant metal, even at temperatures as high as 2000 °C. Although only certain molten salts and halogens are corrosive to solid iridium, finely divided iridium dust is much more reactive and can be flammable.
Latin name: Iridium
Atomic Number
77
Atomic Mass
193 g/mol
Phase (STP)
Solid
Electron Config.
[Xe] 4f¹⁴ 5d⁷ 6s²
General
SymbolIr
Atomic Number77
Atomic Mass193 g/mol
CategoryTransition Metal
Group9
Period6
Blockd-block
Electron Configuration[Xe] 4f¹⁴ 5d⁷ 6s²
Valence Electrons9
Coloursilvery-white metallic
Appearancesilvery white
CAS NumberCAS7440-66-6
Physical Properties
Phase (STP)Solid
Density22.56 g/cm³
Melting Point2445.85°C · 4434.53°F · 2719.00 K
Boiling Point4427.85°C · 8002.13°F · 4701.00 K
Atomic Properties
Atomic Radius202 pm
Electronegativity2.2 Pauling
Ionization Energy880 kJ/mol
Oxidation States+1, +2, +3, +4, +6
Ion ChargeIr+/Ir2+/Ir3+/Ir4+/Ir6+
Thermodynamic
Molar Heat25.1 J/(mol·K)
Crystal Structure
Crystal Structureface-centered cubic
Mechanical Properties
Mohs Hardness6.5
Nuclear & Hazards
Half-lifestable
Abundance
In Universe0.000002%
In Sun0.0000018%
In Earth's Crust0.000002%
Discovery & History
Discovery Year1803
Discovered BySmithson Tennant
Country of DiscoveryEngland
Isotopes of Iridium
| Isotope | Abundance | Half-life | Decay |
|---|---|---|---|
| Ir-191 | 37.3% | Stable | — |
| Ir-193 | 62.7% | Stable | — |