Iridium
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.
Gallery
Unknown authorUnknown author, CC BY 1.0 <https://creativecommons.org/licenses/by/1.0>, via Wikimedia Commons, source: https://images-of-elements.com/iridium.php
Physical Propertiesmass · density · phase · crystal
Atomic Mass
192.2170Da
Density
22.5622g/cm³
Phase (STP)
Solid
Melting Point
2719.2K
Boiling Point
4701.1K
Molar Heat
0.1310J/(mol·K)
Crystal Structure
FCC
Lattice Constant
3.840Å
Atomic Radiiatomic · covalent · van der Waals
Atomic (Empirical)
135.00pm
Covalent
122.00pm
Van der Waals
213.00pm
Electronic Propertieselectronegativity · ionization · affinity
Electron Configuration
[Xe] 4f14 5d7 6s2
Electron Shells
2, 8, 18, 32, 15, 2
Electronegativity
2.20Pauling
Electron Affinity
1.6kJ/mol
1st Ionization Energy
9.0kJ/mol
Oxidation States
-3, -1, 0, +1, +2, +3, +4, +5, +6
Orbital DiagramAufbau · Hund's rule · Pauli exclusion
Full: 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 5s2 5p6 4f14 5d7 6s2Short: [Xe] 4f14 5d7 6s2
Ionization Energies (77 known)
Emission Spectrumvisible range · characteristic spectral lines
Abundanceby mass
Log scale · ppm = parts per million by mass
Biological Role
No known biological role. Iridium-rich clay layer marks the K-Pg extinction event.
Discovery
Discovered By
S.Tenant, A.F.Fourcory, L.N.Vauquelin, H.V.Collet-Descoltils
Named By
—
Year
1804
Nuclear Data
Known Isotopes
43
Stable Isotopes
3
Stable Mass Numbers
163, 191, 193
Natural isotopic abundance (IUPAC recommended values)
Isotopes of Ir43 known
| Nuclide | Z | N | Mass (AMU) | Half-life | Decay | Jπ | Abundance |
|---|---|---|---|---|---|---|---|
| 163Irstable | 77 | 86 | 162.994299 | Stable | p | 1/2+ | — |
| 164Ir | 77 | 87 | 163.991966 | Unknown | p, α, β⁺ | 2- | — |
| 165Ir | 77 | 88 | 164.987552 | Unknown | p, α | 1/2+ | — |
| 191Irstable | 77 | 114 | 190.960591 | Stable | stable (1%) | 3/2+ | 3730.0000% |
| 193Irstable | 77 | 116 | 192.962924 | Stable | stable (1%) | 3/2+ | 6270.0000% |
| 203Ir | 77 | 126 | 202.984573 | Unknown | β⁻ | 3/2+ | — |
| 204Ir | 77 | 127 | 203.989726 | Unknown | β⁻, β⁻n | — | — |
| 205Ir | 77 | 128 | 204.993988 | Unknown | β⁻, β⁻n | 3/2+ | — |