Iridium

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Iridium
77Ir
Rh

Ir

Mt
osmiumiridiumplatinum
Appearance
sillery white
Twa square pieces o gray foil
General properties
Name, seembol, nummer iridium, Ir, 77
Pronunciation /ɨˈrɪdiəm/
i-RID-ee-əm
Element category transeetion metal
Group, period, block 9, 6, d
Staundart atomic wicht 192.217
Electron confeeguration [Xe] 4f14 5d7 6s2
2, 8, 18, 32, 15, 2
Electron shells of iridium (2, 8, 18, 32, 15, 2)
History
Discovery Smithson Tennant (1803)
First isolation Smithson Tennant (1803)
Physical properties
Phase solid
Density (near r.t.) 22.56 g·cm−3
Liquid density at m.p. 19 g·cm−3
Meltin pynt 2739 K, 2466 °C, 4471 °F
Boilin pynt 4701 K, 4428 °C, 8002 °F
Heat o fusion 41.12 kJ·mol−1
Heat o vaporization 563 kJ·mol−1
Molar heat capacity 25.10 J·mol−1·K−1
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, 8
Electronegativity 2.20 (Pauling scale)
Ionization energies 1st: 880 kJ·mol−1
2nd: 1600 kJ·mol−1
Atomic radius 136 pm
Covalent radius 141±6 pm
Miscellanea
Crystal structure face-centered cubic
Iridium has a face-centered cubic crystal structure
Magnetic orderin paramagnetic[1]
Electrical resistivity (20 °C) 47.1 nΩ·m
Thermal conductivity 147 W·m−1·K−1
Thermal expansion 6.4 µm/(m·K)
Speed of sound (thin rod) (20 °C) 4825 m·s−1
Young's modulus 528 GPa
Shear modulus 210 GPa
Bulk modulus 320 GPa
Poisson ratio 0.26
Mohs hairdness 6.5
Vickers hairdness 1760 MPa
Brinell hairdness 1670 MPa
CAS registry nummer 7439-88-5
Most stable isotopes
Main article: Isotopes o iridium
iso NA hauf-life DM DE (MeV) DP
188Ir syn 1.73 d ε 1.64 188Os
189Ir syn 13.2 d ε 0.532 189Os
190Ir syn 11.8 d ε 2.000 190Os
191Ir 37.3% - (α) 2.0839 187Re
192Ir syn 73.827 d β 1.460 192Pt
ε 1.046 192Os
192m2Ir syn 241 y IT 0.161 192Ir
193Ir 62.7% - (α) 1.0173 189Re
193mIr syn 10.5 d IT 0.080 193Ir
194Ir syn 19.3 h β 2.247 194Pt
194m2Ir syn 171 d IT - 194Ir
Decay modes in parentheses are predictit, but hae nae yet been observed
· r

Iridium is the chemical element wi seembol Ir an atomic nummer 77. A very hard, brittle, sillery-white transeetion metal o the platinum faimily, iridium is the seicont-densest element (efter osmium) an is the maist corrosion-resistant metal, even at temperaturs as heich as 2000 °C. Altho anly certain molten sauts an halogens are corrosive tae solid iridium, finely divided iridium dust is much mair reactive an can be flammable.

References[eedit | eedit soorce]

  1. Magnetic susceptibility of the elements and inorganic compounds, in Lide, D. R., ed. (2005). CRC Handbook of Chemistry and Physics (86th ed.). Boca Raton (FL): CRC Press. ISBN 0-8493-0486-5.