CAS Number7439-99-8
PubChem CIDna
Atomic Radius155
Atomic Volume11.62
Atomic Weight[237]
Boiling Point4,000
Bulk Modulus
Crystal StructureSimple Orthorhombic
Covalent Radius190
Electrical Resistivity
Electron Configuration[Rn] 5f4 6d1 7s2
Electrons per shell2, 8, 18, 32, 22, 9, 2
Heat of Fusion10
Heat of Vaporization335
Ionization Potential6.266
Magnetic Ordering
Magnetic Susceptibility
Mass Number93
Melting Point637
Atomic Number237
Oxidation States3, 4, 5, 6, 7
Poisson Ratio
Shear Modulus
Specific Heat Capacity-
Thermal Conductivity0.063
Van der Waals radius
Young's Modulus
Abundance in Earth's crustna
Abundance in Universena
Np Neptunium 93 (237) 7 f 93 640.0 3900.0 [Rn] 5f4 6d1 7s2 2 8 18 32 22 9 2 20.2 None Silver Orthorhombic 1.4 {"1":"604.5"} 605 +5,3,4,6 1.3 21.1 6.3 1 2.1455×1066y AlphaEmission Solid, Conductor, Actinide, Radioactive, Synthetic nep-TOO-ni-em Rare, silvery radioactive metal. It has no significant commercial applications. Produced by bombarding uranium with slow neutrons. AFo96BkYNdQ Neptunium
Iridium was discovered in 1803 by English chemist Smithson Tennant in London.

Chemists who studied platinum dissolved it in aqua regia to create soluble salts and observed a small amount of a dark, insoluble residue.

Smithson Tennant analyzed the insoluble residue and concluded that it must contain a new metal. From the Latin word iris meaning rainbow 93 1940 Edwin M. McMillan and P. H. Abelson USA Named after "the planet Neptune"

Isotopes of Iridium

Standard Atomic Weight


Stable Isotopes

Unstable Isotopes

225Np 226Np 227Np 228Np 229Np 230Np 231Np 232Np 233Np 234Np 235Np 236Np 237Np 238Np 239Np 240Np 241Np 242Np 243Np 244Np

Iridium is considered to be of low toxicity
Iridium is the most corrosion-resistant metal known
Iridium is used in making crucibles and other equipment that is used at high temperatures.

Iridium is also used as a hardening agent in platinum alloys.

Its resistance to arc erosion makes iridium alloys ideal for electrical contacts for spark plugs.

Radioactive isotopes of iridium are used in radiation therapy for the treatment of cancer.