Difference between revisions of "Iridium"

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'''Iridium''' is the chemical element with symbol '''Ir''' and atomic number 77. It is a transitional group metal, part of the so called platinum group metals. Iridium is one of the rarest elements in the Earth's crust, with annual production and consumption of only three metric tonnes.
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{{Infobox element
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|image name=Iridium granules at Johnson Matthey noble metal plant.jpg
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|image name comment=Iridium metal granules in the hands of prof. Martyn Poliakoff
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<!-- General properties -->
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|name=Iridium
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|symbol=Ir
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|pronounce=
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|pronounce ref=
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|pronounce comment=
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|pronounce 2=
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|alt name=
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|alt names=
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|allotropes=
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|appearance=Silvery shiny metal
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<!-- Periodic table -->
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|above=[[Rhodium|Rh]]
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|below=Mt
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|left= [[Osmium]]
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|right=[[Platinum]]
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|number=77
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|atomic mass= 192.217(3)
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|atomic mass 2=
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|atomic mass ref=
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|atomic mass comment=
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|series=
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|series ref=
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|series comment=
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|series color=
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|group=9
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|group ref=
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|group comment=
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|period=6
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|period ref=
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|period comment=
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|block=d
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|block ref=
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|block comment=
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|electron configuration= [Xe] 4f<sup>14</sup> 5d<sup>7</sup> 6s<sup>2</sup>
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|electron configuration ref=
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|electron configuration comment=
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|electrons per shell=2, 8, 18, 32, 15, 2
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|electrons per shell ref=
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|electrons per shell comment=
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<!-- Physical properties -->
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|physical properties comment=
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|color=Silvery-white
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|phase=Solid
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|phase ref=
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|phase comment=
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|melting point K=2719
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|melting point C=2446
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|melting point F=4435
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|melting point ref=
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|melting point comment=
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|boiling point K=4403
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|boiling point C=4130
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|boiling point F=​7466
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|boiling point ref=
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|boiling point comment=
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|sublimation point K=
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|sublimation point C=
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|sublimation point F=
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|sublimation point ref=
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|sublimation point comment=
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|density gplstp=
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|density gplstp ref=
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|density gplstp comment=
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|density gpcm3nrt=22.56
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|density gpcm3nrt ref=
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|density gpcm3nrt comment=
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|density gpcm3nrt 2=
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|density gpcm3nrt 3=
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|density gpcm3mp=19
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|density gpcm3mp comment=
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|density gpcm3bp=
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|density gpcm3bp ref=
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|density gpcm3bp comment=
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|molar volume=
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|molar volume unit =
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|molar volume ref=
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|molar volume comment=
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|triple point K=
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|triple point kPa=
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|triple point ref=
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|triple point comment=
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|triple point K 2=
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|critical point K=
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|critical point MPa=
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|critical point ref=
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|critical point comment=
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|heat fusion=41.12
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|heat fusion ref=
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|heat fusion comment=
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|heat fusion 2=
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|heat fusion 2 ref=
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|heat fusion 2 comment=
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|heat vaporization=564
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|heat vaporization ref=
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|heat vaporization comment=
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|heat capacity=25.1
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|heat capacity ref=
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|heat capacity comment=
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|heat capacity 2=
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|heat capacity 2 ref=
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|heat capacity 2 comment=
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|vapor pressure 1=2713
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|vapor pressure 10=2957
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|vapor pressure 100=3252
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|vapor pressure 1 k=3614
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|vapor pressure 10 k=4069
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|vapor pressure 100 k=4659
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|vapor pressure ref=
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|vapor pressure comment=
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|vapor pressure 1 2=
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|vapor pressure 10 2=
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|vapor pressure 100 2=
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|vapor pressure 1 k 2=
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|vapor pressure 10 k 2=
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|vapor pressure 100 k 2=
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|vapor pressure 2 ref=
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|vapor pressure 2 comment=
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<!-- Atomic properties -->
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|atomic properties comment=
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|oxidation states=−3, −1, 0, 1, 2, '''3''', '''4''', 5, 6, 7, 8, 9
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|oxidation states ref=
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|oxidation states comment=
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|electronegativity=2.20
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|electronegativity ref=
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|electronegativity comment=
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|ionization energy 1=880
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|ionization energy 1 ref=
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|ionization energy 1 comment=
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|ionization energy 2=1600
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|ionization energy 2 ref=
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|ionization energy 2 comment=
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|ionization energy 3=
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|ionization energy 3 ref=
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|ionization energy 3 comment=
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|number of ionization energies=
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|ionization energy ref=
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|ionization energy comment=
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|atomic radius=136
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|atomic radius ref=
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|atomic radius comment=
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|atomic radius calculated=
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|atomic radius calculated ref=
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|atomic radius calculated comment=
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|covalent radius=141±6
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|covalent radius ref=
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|covalent radius comment=
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|Van der Waals radius=
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|Van der Waals radius ref=
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|Van der Waals radius comment=
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<!-- Miscellanea -->
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|crystal structure=
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|crystal structure prefix=
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|crystal structure ref=
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|crystal structure comment=Face-centered cubic (fcc)
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|crystal structure 2=
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|crystal structure 2 prefix=
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|crystal structure 2 comment=
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|speed of sound=
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|speed of sound ref=
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|speed of sound comment=
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|speed of sound rod at 20=4825
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|speed of sound rod at 20 ref=
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|speed of sound rod at 20 comment=
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|speed of sound rod at r.t.=
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|speed of sound rod at r.t. ref=
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|speed of sound rod at r.t. comment=
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|thermal expansion=6.4
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|thermal expansion ref=
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|thermal expansion comment=
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|thermal expansion at 25=
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|thermal expansion at 25 ref=
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|thermal expansion at 25 comment=
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|thermal conductivity=147
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|thermal conductivity ref=
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|thermal conductivity comment=
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|thermal conductivity 2=
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|thermal diffusivity=
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|electrical resistivity=
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|electrical resistivity unit prefix=
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|electrical resistivity comment=
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|electrical resistivity at 0=
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|electrical resistivity at 0 ref=
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|electrical resistivity at 0 comment=
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|electrical resistivity at 20=4.71·10<sup>-8</sup>
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|electrical resistivity at 20 ref=
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|electrical resistivity at 20 comment=
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|band gap=
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|band gap ref=
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|band gap comment=
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|Curie point K=
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|Curie point ref=
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|Curie point comment=
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|magnetic ordering=Paramagnetic
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|magnetic ordering ref=
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|magnetic ordering comment=
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|tensile strength=
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|tensile strength ref=
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|tensile strength comment=
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|Young's modulus=528
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|Young's modulus ref=
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|Young's modulus comment=
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|Shear modulus=210
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|Shear modulus ref=
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|Shear modulus comment=
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|Bulk modulus=320
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|Bulk modulus ref=
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|Bulk modulus comment=
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|Poisson ratio=0.26
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|Poisson ratio ref=
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|Poisson ratio comment=
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|Mohs hardness=6.5
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|Mohs hardness ref=
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|Mohs hardness comment=
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|Mohs hardness 2=
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|Mohs hardness 2 ref=
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|Mohs hardness 2 comment=
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|Vickers hardness=1760–2200
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|Vickers hardness ref=
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|Vickers hardness comment=
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|Brinell hardness=1670
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|Brinell hardness ref=
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|Brinell hardness comment=
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|CAS number=7439-88-5
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|CAS number ref=
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|CAS number comment=
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<!-- History -->
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|naming=
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|predicted by=
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|discovered by=
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|discovery date=
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|first isolation by=
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|first isolation date=
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|discovery and first isolation by=Smithson Tennant (1803)
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|named by=
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|named date=
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|history comment label=
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|history comment=
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<!-- Isotopes -->
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|isotopes=
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|isotopes comment=
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|engvar=
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}}
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'''Iridium''' is the chemical element with symbol '''Ir''' and atomic number 77. It is a transitional group metal, part of the so called platinum group metals. Iridium is one of the rarest elements in the Earth's crust, with annual production and consumption of only three metric tonnes, making it an expensive metal. However, despite the fact that iridium is rarer than platinum and gold, it is somewhat cheaper due to peculiarities of the precious metal market.
  
 
==Properties==
 
==Properties==
 
===Chemical===
 
===Chemical===
Iridium is the most corrosion resistant metal, even at high temperatures. At standard conditions, no chemical compound can attack it. Finely divided however, it is more reactive. At high temperatures, molten [[sodium cyanide]] and [[potassium cyanide]] will attack iridium, as well as [[oxygen]] and [[fluorine]].
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Iridium is the most corrosion resistant metal, even at high temperatures. At standard conditions, no chemical compound can attack it in bulk form. Finely divided however, it is more reactive. At high temperatures, molten [[sodium cyanide]] and [[potassium cyanide]] will attack iridium, as well as [[oxygen]] and [[fluorine]].
  
 
Iridium tends to form mixed-valence compounds, most notably [[iridum(IV) chloride]] (whose name is particularly unusual).
 
Iridium tends to form mixed-valence compounds, most notably [[iridum(IV) chloride]] (whose name is particularly unusual).
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Iridium can be found in certain high-performance car spark plugs, in the tip of the electric contact. Because it's immune to most corrosive substances, it's recommended to dissolve the welding around the iridium. It is not much, but being very dense, just a few spark tips can build up a significant quantity.
 
Iridium can be found in certain high-performance car spark plugs, in the tip of the electric contact. Because it's immune to most corrosive substances, it's recommended to dissolve the welding around the iridium. It is not much, but being very dense, just a few spark tips can build up a significant quantity.
  
Lastly, iridium can be bought as bullions and coins, though in recent years it has risen to 20$/gram.
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Lastly, iridium can be bought as bullions and coins, though in recent years it's price has risen to 46 $/gram.
  
Iridium's high melting point and chemical resistance allows it to be used in the creation of high-performance crucibles which, unlike the ceramic ones, are very thin, thus reducing the amount of iridium used. Such crucibles are used for single crystal growth.
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Iridium's high melting point and chemical resistance allows it to be used in the creation of high-performance crucibles which, unlike the ceramic ones, are very thin, thus reducing the amount of iridium used. Such crucibles are widely used for single crystal growth.
  
 
==Preparation==
 
==Preparation==
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[[Category:D-block]]
 
[[Category:D-block]]
 
[[Category:Noble metals]]
 
[[Category:Noble metals]]
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[[Category:Inert chemicals]]

Latest revision as of 17:00, 28 February 2019

Iridium,  77Ir
Iridium granules at Johnson Matthey noble metal plant.jpg
Iridium metal granules in the hands of prof. Martyn Poliakoff
General properties
Name, symbol Iridium, Ir
Appearance Silvery shiny metal
Iridium in the periodic table
Rh

Ir

Mt
OsmiumIridiumPlatinum
Atomic number 77
Standard atomic weight (Ar) 192.217(3)
Group, block , d-block
Period period 6
Electron configuration [Xe] 4f14 5d7 6s2
per shell
2, 8, 18, 32, 15, 2
Physical properties
Silvery-white
Phase Solid
Melting point 2719 K ​(2446 °C, ​4435 °F)
Boiling point 4403 K ​(4130 °C, ​​7466 °F)
Density near r.t. 22.56 g/cm3
when liquid, at  19 g/cm3
Heat of fusion 41.12 kJ/mol
Heat of 564 kJ/mol
Molar heat capacity 25.1 J/(mol·K)
 pressure
Atomic properties
Oxidation states −3, −1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9
Electronegativity Pauling scale: 2.20
energies 1st: 880 kJ/mol
2nd: 1600 kJ/mol
Atomic radius empirical: 136 pm
Covalent radius 141±6 pm
Miscellanea
Crystal structure ​Face-centered cubic (fcc)
Speed of sound thin rod 4825 m/s (at 20 °C)
Thermal expansion 6.4 µm/(m·K)
Thermal conductivity 147 W/(m·K)
Electrical resistivity 4.71·10-8 Ω·m (at 20 °C)
Magnetic ordering Paramagnetic
Young's modulus 528 GPa
Shear modulus 210 GPa
Bulk modulus 320 GPa
Poisson ratio 0.26
Mohs hardness 6.5
Vickers hardness 1760–2200 MPa
Brinell hardness 1670 MPa
CAS Registry Number 7439-88-5
Discovery and first isolation Smithson Tennant (1803)
· references

Iridium is the chemical element with symbol Ir and atomic number 77. It is a transitional group metal, part of the so called platinum group metals. Iridium is one of the rarest elements in the Earth's crust, with annual production and consumption of only three metric tonnes, making it an expensive metal. However, despite the fact that iridium is rarer than platinum and gold, it is somewhat cheaper due to peculiarities of the precious metal market.

Properties

Chemical

Iridium is the most corrosion resistant metal, even at high temperatures. At standard conditions, no chemical compound can attack it in bulk form. Finely divided however, it is more reactive. At high temperatures, molten sodium cyanide and potassium cyanide will attack iridium, as well as oxygen and fluorine.

Iridium tends to form mixed-valence compounds, most notably iridum(IV) chloride (whose name is particularly unusual).

Iridium will form alloys with metals, such as osmium (osmiridium) and iron.

Iridium's organometallic chemistry is extensively studied, as iridium forms very stable bonds with carbon.

Physical

Iridium is a silvery white, very hard metal. It has excellent mechanical properties, which makes it difficult to work with. It's high melting point of 2446 °C makes it difficult to melt and cast, so powdered metallurgy is usually employed. It is the only metal to maintain good mechanical properties in air at temperatures above 1600 °C, making it useful as a high temperature catalyst. It is the second densest element after osmium, with a value of 22.56 g/cm3. Because of this property, most of the elemental iridium has sunk in the Earth crust.

Availability

In nature it usually found together with osmium, usually in meteorites. However due to it's low concentration, it's not a particularly good source for the amateur chemist.

Iridium can be found in certain high-performance car spark plugs, in the tip of the electric contact. Because it's immune to most corrosive substances, it's recommended to dissolve the welding around the iridium. It is not much, but being very dense, just a few spark tips can build up a significant quantity.

Lastly, iridium can be bought as bullions and coins, though in recent years it's price has risen to 46 $/gram.

Iridium's high melting point and chemical resistance allows it to be used in the creation of high-performance crucibles which, unlike the ceramic ones, are very thin, thus reducing the amount of iridium used. Such crucibles are widely used for single crystal growth.

Preparation

As it sits at the bottom of the metal reactivity series, it can be reduced very easy from it's compounds.

Projects

  • Organoiridium compounds
  • Single crystal growth in iridium crucibles

Handling

Safety

Being the least reactive metal, iridium is non-toxic. Finely divided iridium powder can be hazardous to handle, as it is an irritant and may ignite in air.

Storage

Bulk iridium does not require any special storage. Powdered iridium should be stored in closed containers.

Disposal

Due to iridium's rarity and price, it's best to recycle it.

References

Relevant Sciencemadness threads