Ir

Iridium

Identification

CAS Number: 7439-88-5

Discovery Year: 1804

Discoverer: S.Tenant, A.F.Fourcory, L.N.Vauquelin, H.V.Collet-Descoltils

Discovery Location: England/France

Properties

Atomic Mass: 192.217 →Density: 22.5622 g/cm³ →

Crust Abundance: 0.001 mg/kg

Crystal Structure: FCC

Atomic Dimensions

Atomic Radius: 135 pm →

Atomic Radius (Rahm): 240 pm

Covalent Radius: 141 pm →

Van der Waals Radius: 213 pm

Metallic Radius: 127 pm

Atomic Volume: 8.54 cm³/mol

Lattice Constant: 3.84 Å

Thermodynamics

Melting Point: 2683 K →Boiling Point: 4403 K →Specific Heat: 0.133 J/(g·K) →Thermal Conductivity: 147 W/(m·K) →Heat of Fusion: 27.61 kJ/mol →Heat of Vaporization: 604 kJ/mol →

Heat of Formation: 669 kJ/mol

Electronic Structure

Electron Config: [Xe] 4f14 5d7 6s2

Block: d

Period: 6 →Group: 9 →Electronegativity: 2.2 →Electron Affinity: 1.5638 eV →

Oxidation States: -1, 0, +1, +2, +3, +4, +6

Abundance & Geochemistry

Crust Abundance: 0.001 mg/kg

Geochemical Class: noble metal

Goldschmidt Class: siderophile

About

Very hard and brittle, silvery metallic transition element. It has a yellowish cast to it. Salts of iridium are highly colored. It is the most corrosion resistant metal known, not attacked by any acid, but is attacked by molten salts. There are two natural isotopes of iridium, and 4 radioisotopes, the most stable being Ir-192 with a half-life of 73.83 days. Ir-192 decays into Platinum, while the other radioisotopes decay into Osmium. Iridium is used in high temperature apparatus, electrical contacts, and as a hardening agent for platinumpy. Discovered in 1803 by Smithson Tennant in England. The name comes from the Greek word iris, which means rainbow. Iridium metal is generally non-toxic due to its relative unreactivity, but iridium compounds should be considered highly toxic.

Isotopes

Ir-193 193 62.70%

Ir-191 191 37.30%