Iridium

77
Ir
Group
9
Period
6
Block
d
Protons
Electrons
Neutrons
77
77
115
General Properties
Atomic Number
77
Atomic Weight
192.217
Mass Number
192
Category
Transition metals
Colour
Silver
Radioactive
No
From the Latin word iris meaning rainbow
Crystal Structure
Face Centered Cubic
History
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.
Electrons per shell
2, 8, 18, 32, 15, 2
Electron Configuration
[Xe] 4f14 5d7 6s2
Ir
Iridium is the most corrosion-resistant metal known
Physical Properties
Phase
Solid
Density
22.56 g/cm3
Melting Point
2739.15 K | 2466 °C | 4470.8 °F
Boiling Point
4701.15 K | 4428 °C | 8002.4 °F
Heat of Fusion
26 kJ/mol
Heat of Vaporization
560 kJ/mol
Specific Heat Capacity
0.131 J/g·K
Abundance in Earth's crust
4×10-8%
Abundance in Universe
2×10-7%
Pieces
Image Credits: Images-of-elements
Pieces of pure iridium
CAS Number
7439-88-5
PubChem CID Number
23924
Atomic Properties
Atomic Radius
136 pm
Covalent Radius
141 pm
Electronegativity
2.2 (Pauling scale)
Ionization Potential
8.967 eV
Atomic Volume
8.54 cm3/mol
Thermal Conductivity
1.47 W/cm·K
Oxidation States
-3, -1, 1, 2, 3, 4, 5, 6, 7, 8, 9
Applications
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.
Iridium is considered to be of low toxicity
Isotopes
Stable Isotopes
191Ir, 193Ir
Unstable Isotopes
164Ir, 165Ir, 166Ir, 167Ir, 168Ir, 169Ir, 170Ir, 171Ir, 172Ir, 173Ir, 174Ir, 175Ir, 176Ir, 177Ir, 178Ir, 179Ir, 180Ir, 181Ir, 182Ir, 183Ir, 184Ir, 185Ir, 186Ir, 187Ir, 188Ir, 189Ir, 190Ir, 192Ir, 194Ir, 195Ir, 196Ir, 197Ir, 198Ir, 199Ir