Iridium is the chemical element wi seembol Ir an atomic nummer 77. A vera haurd, brickle, siller-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. Tho anerly certaint molten sauts an halogens is corrosive tae solit iridium, finely dividit iridium dust is a fair bit mair reactive an can be flammable.
Iridium, 77 Iridium Pronunciation (ih-RID -ee-əm Appearance sillery white Standard atomic weight A r, std (Ir) 7002192217000000000♠ 192.217(2)[1] Iridium in the periodic cairt Atomic nummer (Z ) 77 Group group 9 Period period 6 Block d-block Element category Transeetion metalElectron confeeguration [Xe ] 4f14 5d7 6s2 Electrons per shell 2, 8, 18, 32, 15, 2 Pheesical properties Phase at STP solid Meltin pynt 2719 K (2446 °C, 4435 °F) Bylin pynt 4403 K (4130 °C, 7466 °F) Density (near r.t. ) 22.56 g/cm3 when liquid (at m.p. ) 19 g/cm3 Heat o fusion 41.12 kJ/mol Heat o vapourisation 564 kJ/mol Molar heat capacity 25.10 J/(mol·K) Vapour pressur 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 [2] Electronegativity Pauling scale: 2.20 Ionisation energies 1st: 880 kJ/mol 2nd: 1600 kJ/mol Atomic radius empirical: 136 pm Covalent radius 141±6 pm Colour lines in a spectral range Spectral lines o iridium Ither properties Naitural occurrence primordial Creestal structur face-centred cubic[[File:face-centred cubic|frameless|alt=Face-centred cubic creestal structur for iridium|upright=0.23|Face-centred cubic creestal structur for iridium]]
Speed o soond thin rod 4825 m/s (at 20 °C) Thermal expansion 6.4 µm/(m·K) Thermal conductivity 147 W/(m·K) Electrical resistivity 47.1 nΩ·m (at 20 °C) Magnetic orderin paramagnetic[3] Magnetic susceptibility +25.6·10−6 cm3 /mol (298 K)[4] Young's modulus 528 GPa Shear modulus 210 GPa Bulk modulus 320 GPa Poisson ratio 0.26 Mohs haurdness 6.5 Vickers haurdness 1760–2200 MPa Brinell haurdness 1670 MPa CAS Nummer 7439-88-5 History Diskivery an first isolation Smithson Tennant (1803) Main isotopes o iridium Isotope Abundance Hauf-life (t 1/2 ) Decay mode Product 188 Irsyn 1.73 d ε 188 Os189 Irsyn 13.2 d ε 189 Os190 Irsyn 11.8 d ε 190 Os191 Ir37.3% stable 192 Irsyn 73.827 d β− 192 Ptε 192 Os192m2 Irsyn 241 y IT 192 Ir193 Ir62.7% stable 193m Irsyn 10.5 d IT 193 Ir194 Irsyn 19.3 h β− 194 Pt194m2 Irsyn 171 d IT 194 Ir
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