Iridium,  77Ir
Pieces of pure iridium
General properties
Pronunciation/ɪˈrɪdiəm/ (i-RID-ee-əm)
Appearancesilvery white
Standard atomic weight (Ar, standard)192.217(2)[1]
Iridium in the periodic table
[[Hydrogen|Hydrogen [[Helium|Helium
[[Lithium|Lithium [[Beryllium|Beryllium [[Boron|Boron [[Carbon|Carbon [[Nitrogen|Nitrogen [[Oxygen|Oxygen [[Fluorine|Fluorine [[Neon|Neon
[[Sodium|Sodium [[Magnesium|Magnesium [[Aluminium|Aluminium [[Silicon|Silicon [[Phosphorus|Phosphorus [[Sulfur|Sulfur [[Chlorine|Chlorine [[Argon|Argon
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[[Rubidium|Rubidium [[Strontium|Strontium [[Yttrium|Yttrium [[Zirconium|Zirconium [[Niobium|Niobium [[Molybdenum|Molybdenum [[Technetium|Technetium [[Ruthenium|Ruthenium [[Rhodium|Rhodium [[Palladium|Palladium [[Silver|Silver [[Cadmium|Cadmium [[Indium|Indium [[Tin|Tin [[Antimony|Antimony [[Tellurium|Tellurium [[Iodine|Iodine [[Xenon|Xenon
[[Caesium|Caesium [[Barium|Barium [[Lanthanum|Lanthanum [[Cerium|Cerium [[Praseodymium|Praseodymium [[Neodymium|Neodymium [[Promethium|Promethium [[Samarium|Samarium [[Europium|Europium [[Gadolinium|Gadolinium [[Terbium|Terbium [[Dysprosium|Dysprosium [[Holmium|Holmium [[Erbium|Erbium [[Thulium|Thulium [[Ytterbium|Ytterbium [[Lutetium|Lutetium [[Hafnium|Hafnium [[Tantalum|Tantalum [[Tungsten|Tungsten [[Rhenium|Rhenium [[Osmium|Osmium [[Iridium|Iridium [[Platinum|Platinum [[Gold|Gold [[Mercury (element)|Mercury (element) [[Thallium|Thallium [[Lead|Lead [[Bismuth|Bismuth [[Polonium|Polonium [[Astatine|Astatine [[Radon|Radon
[[Francium|Francium [[Radium|Radium [[Actinium|Actinium [[Thorium|Thorium [[Protactinium|Protactinium [[Uranium|Uranium [[Neptunium|Neptunium [[Plutonium|Plutonium [[Americium|Americium [[Curium|Curium [[Berkelium|Berkelium [[Californium|Californium [[Einsteinium|Einsteinium [[Fermium|Fermium [[Mendelevium|Mendelevium [[Nobelium|Nobelium [[Lawrencium|Lawrencium [[Rutherfordium|Rutherfordium [[Dubnium|Dubnium [[Seaborgium|Seaborgium [[Bohrium|Bohrium [[Hassium|Hassium [[Meitnerium|Meitnerium [[Darmstadtium|Darmstadtium [[Roentgenium|Roentgenium [[Copernicium|Copernicium [[Nihonium|Nihonium [[Flerovium|Flerovium [[Moscovium|Moscovium [[Livermorium|Livermorium [[Tennessine|Tennessine [[Oganesson|Oganesson


Atomic number (Z)77
Groupgroup 9
Periodperiod 6
Element category  transition metal
Electron configuration[Xe] 4f14 5d7 6s2
Electrons per shell
2, 8, 18, 32, 15, 2
Physical properties
Phase at STPsolid
Melting point2719 K ​(2446 °C, ​4435 °F)
Boiling point4403 K ​(4130 °C, ​7466 °F)
Density (near r.t.)22.56 g/cm3
when liquid (at m.p.)19 g/cm3
Heat of fusion41.12 kJ/mol
Heat of vaporization564 kJ/mol
Molar heat capacity25.10 J/(mol·K)
Vapor pressure
P (Pa) 1 10 100 1 k 10 k 100 k
at T (K) 2713 2957 3252 3614 4069 4659
Atomic properties
Oxidation states−3, −1, 0, +1, +2, +3, +4, +5, +6, +7, +8, +9[2]
ElectronegativityPauling scale: 2.20
Ionization energies
  • 1st: 880 kJ/mol
  • 2nd: 1600 kJ/mol
Atomic radiusempirical: 136 pm
Covalent radius141±6 pm
Color lines in a spectral range
Spectral lines of iridium
Other properties
Crystal structureface-centered cubic (fcc)
Face-centered cubic crystal structure for iridium
Speed of sound thin rod4825 m/s (at 20 °C)
Thermal expansion6.4 µm/(m·K)
Thermal conductivity147 W/(m·K)
Electrical resistivity47.1 nΩ·m (at 20 °C)
Magnetic orderingparamagnetic[3]
Magnetic susceptibility+25.6·10−6 cm3/mol (298 K)[4]
Young's modulus528 GPa
Shear modulus210 GPa
Bulk modulus320 GPa
Poisson ratio0.26
Mohs hardness6.5
Vickers hardness1760–2200 MPa
Brinell hardness1670 MPa
CAS Number7439-88-5
Discovery and first isolationSmithson Tennant (1803)
Main isotopes of iridium
Iso­tope Abun­dance Half-life (t1/2) Decay mode Pro­duct
188Ir syn 1.73 d ε 188Os
189Ir syn 13.2 d ε 189Os
190Ir syn 11.8 d ε 190Os
191Ir 37.3% stable
192Ir syn 73.827 d β 192Pt
ε 192Os
192m2Ir syn 241 y IT 192Ir
193Ir 62.7% stable
193mIr syn 10.5 d IT 193Ir
194Ir syn 19.3 h β 194Pt
194m2Ir syn 171 d IT 194Ir
| references
Os ←

i'box Os

Ir E
→ Pt

i'box Pt

Data sets read by {{Infobox element}}
Name and identifiers
Top image
  image caption
  image alt
Category (enwiki)
Standard atomic weight
  most stable isotope
Oxidation states
Spectral lines image


  1. Meija, J.; മറ്റുള്ളവർക്കൊപ്പം. (2016). "Atomic weights of the elements 2013 (IUPAC Technical Report)". Pure and Applied Chemistry. 88 (3): 265–91. doi:10.1515/pac-2015-0305.
  2. 2.0 2.1 Wang, Guanjun; Zhou, Mingfei; Goettel, James T.; Schrobilgen, Gary G.; Su, Jing; Li, Jun; Schlöder, Tobias; Riedel, Sebastian (2014). "Identification of an iridium-containing compound with a formal oxidation state of IX". Nature. 514: 475–477. Bibcode:2014Natur.514..475W. doi:10.1038/nature13795. PMID 25341786.
  3. Lide, D. R., ed. (2005). "Magnetic susceptibility of the elements and inorganic compounds". CRC Handbook of Chemistry and Physics (PDF) (86th ed.). Boca Raton (FL): CRC Press. ISBN 0-8493-0486-5.
  4. Weast, Robert (1984). CRC, Handbook of Chemistry and Physics. Boca Raton, Florida: Chemical Rubber Company Publishing. pp. E110. ISBN 0-8493-0464-4.


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