Difference between revisions of "Argon"

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[[File:Solid_argon_melting_and_subliming_The_Royal_Institution.jpg|thumb|300px|Argon, after being frozen with liquid nitrogen, melting and subliming at the same time, at standard conditions.]]
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{{Infobox element
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<!-- top -->
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|image name=Solid_argon_melting_and_subliming_The_Royal_Institution.jpg
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|image alt=
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|image size=300
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|image name comment=Argon, after being frozen with liquid nitrogen, melting and subliming at the same time, at standard conditions.
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|image name 2=
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|image alt 2=
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|image size 2=
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|image name 2 comment=
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<!-- General properties -->
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|name=Argon
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|symbol=Ar
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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=Colorless gas exhibiting a lilac/violet glow when placed in an electric field
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<!-- Periodic table -->
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|above=[[Neon|Ne]]
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|below=[[Krypton|Kr]]
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|left=[[Chlorine]]
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|right=[[Potassium]]
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|number=18
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|atomic mass=39.948(1)
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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=Noble gasses
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|series ref=
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|series comment=
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|series color=
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|group=18
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|group ref=
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|group comment=
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|period=3
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|period ref=
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|period comment=
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|block= p-block
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|block ref=
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|block comment=
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|electron configuration=[Ne] 3s<sup>2</sup> 3p<sup>6</sup>
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|electron configuration ref=
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|electron configuration comment=
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|electrons per shell=2, 8, 8
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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=Colorless
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|phase=Gas
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|phase ref=
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|phase comment=
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|melting point K=83.81
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|melting point C=−189.34
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|melting point F=308.81
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|melting point ref=
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|melting point comment=
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|boiling point K=87.302
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|boiling point C=−185.848
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|boiling point F=−302.526
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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=1.784
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|density gplstp ref=
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|density gplstp comment=
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|density gpcm3nrt=
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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 2 comment=
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|density gpcm3nrt 3=
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|density gpcm3nrt 3 comment=
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|density gpcm3mp=
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|density gpcm3mp ref=
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|density gpcm3mp comment=
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|density gpcm3bp=1.3954
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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=83.8058
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|triple point kPa=68.89
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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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|triple point kPa 2=
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|triple point 2 ref=
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|triple point 2 comment=
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|critical point K=150.687
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|critical point MPa=4.863
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|critical point ref=
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|critical point comment=
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|heat fusion=1.18
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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=6.53
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|heat vaporization ref=
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|heat vaporization comment=
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|heat capacity=20.85
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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=-
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|vapor pressure 10=47
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|vapor pressure 100=53
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|vapor pressure 1 k=61
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|vapor pressure 10 k=71
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|vapor pressure 100 k=87
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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=0
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|oxidation states ref=
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|oxidation states comment=
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|electronegativity=
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|electronegativity ref=
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|electronegativity comment=
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|ionization energy 1=1520.6
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|ionization energy 1 ref=
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|ionization energy 1 comment=
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|ionization energy 2=2665.8
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|ionization energy 2 ref=
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|ionization energy 2 comment=
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|ionization energy 3=3931
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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=
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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=106±10
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|covalent radius ref=
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|covalent radius comment=
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|Van der Waals radius=188
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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 ref=
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|crystal structure 2 comment=
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|speed of sound=323
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|speed of sound ref=
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|speed of sound comment=(gas, at 27 °C)
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|speed of sound rod at 20=
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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. comment=
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|thermal expansion=
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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=17.72×10<sup>−3</sup>
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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 conductivity 2 ref=
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|thermal conductivity 2 comment=
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|thermal diffusivity=
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|thermal diffusivity comment=
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|electrical resistivity=
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|electrical resistivity unit prefix=
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|electrical resistivity ref=
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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=
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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=Diamagnetic
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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=
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|Young's modulus ref=
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|Young's modulus comment=
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|Mohs hardness=
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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=
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|Vickers hardness comment=
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|Brinell hardness=
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|Brinell hardness ref=
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|Brinell hardness comment=
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|CAS number=7440-37-1
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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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|prediction date=
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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 ref=
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|first isolation date=
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|discovery and first isolation by=Lord Rayleigh and William Ramsay (1894)
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|named by=
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|named date ref=
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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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}}
 
'''Argon''' is a noble gas with the symbol '''Ar''' and the atomic number 18. It forms no compounds accessible to the home chemist due to its inertness, which makes it suitable for inert atmospheres.
 
'''Argon''' is a noble gas with the symbol '''Ar''' and the atomic number 18. It forms no compounds accessible to the home chemist due to its inertness, which makes it suitable for inert atmospheres.
  

Revision as of 20:45, 28 September 2017

Argon,  18Ar
Solid argon melting and subliming The Royal Institution.jpg
Argon, after being frozen with liquid nitrogen, melting and subliming at the same time, at standard conditions.
General properties
Name, symbol Argon, Ar
Appearance Colorless gas exhibiting a lilac/violet glow when placed in an electric field
Argon in the periodic table
Ne
↑
Ar
↓
Kr
Chlorine ← Argon → Potassium
Atomic number 18
Standard atomic weight (Ar) 39.948(1)
Group, block , p-block-block
Period period 3
Electron configuration [Ne] 3s2 3p6
per shell
 2, 8, 8
Physical properties
Colorless
Phase Gas
Melting point 83.81 K ​(−189.34 °C, ​308.81 °F)
Boiling point 87.302 K ​(−185.848 °C, ​−302.526 °F)
Density at  (0 °C and 101.325 kPa) 1.784 g/L
when liquid, at  1.3954 g/cm3
Triple point 83.8058 K, ​68.89 kPa
Critical point 150.687 K, 4.863 MPa
Heat of fusion 1.18 kJ/mol
Heat of 6.53 kJ/mol
Molar heat capacity 20.85 J/(mol·K)
 pressure
Atomic properties
Oxidation states 0
energies 1st: 1520.6 kJ/mol
2nd: 2665.8 kJ/mol
3rd: 3931 kJ/mol
Covalent radius 106±10 pm
Van der Waals radius 188 pm
Miscellanea
Crystal structure ​face-centered cubic (fcc)
Speed of sound 323 m/s (gas, at 27 °C)
Thermal conductivity 17.72×10−3 W/(m·K)
Magnetic ordering Diamagnetic
CAS Registry Number 7440-37-1
Discovery and first isolation Lord Rayleigh and William Ramsay (1894)
· references

Argon is a noble gas with the symbol Ar and the atomic number 18. It forms no compounds accessible to the home chemist due to its inertness, which makes it suitable for inert atmospheres.

Properties

Physical

Argon is a colorless, odorless gas at standard conditions, with a boiling point of -185.848 °C and a melting point of −189.34 °C. It is heavier than air, with an density of 1.784 g/L. Unlike nitrogen, argon is 2.5 times more soluble in water, solubility similar to that of oxygen.

Chemical

Argon is chemically inert under most conditions and forms no confirmed stable compounds at room temperature. At 8 K, argon reacts with hydrogen fluoride, on a cesium iodide surface, resulting in argon fluorohydride, HArF, which is stable only under 17 K.

Availability

Argon is used as a shielding gas in welding, so many gas or welding supply stores will sell and rent out cylinders of pure argon or mixtures of argon and carbon dioxide (the more argon in the mixture, the more expensive it is).

A crude form of argon that is accessible to most people can be obtained from light bulbs, which may contain argon or a mixture of argon and nitrogen. This can be done by holding the bulb underwater, and slipping an open plastic bag around the bulb so that no air is in the bag. After sealing the bag, the light bulb can be broken, causing the inert gas inside to rise to the top while still trapped in the bag.

Preparation

Argon can be separated from liquified air, although the process is very consuming and complicated due to argon's narrow liquid temperature range. It's best to buy argon cylinders.

Uses

As it takes no role in any chemistry, argon can be used as an inert atmosphere.

Creating an inert atmosphere in a home chemistry setting is difficult, and not often done. Nitrogen is usually used in the rare case it is attempted, and argon is called upon when nitrogen and carbon dioxide are unsuitable, as both carbon dioxide and nitrogen are cheaper gases than argon. For some processes that cannot be done in either of these atmospheres, the more expensive and difficult-to-find argon must be used. As argon is heavier than air, any container that is supposed to hold an argon atmosphere should have the opening above.

Argon is the choice in Schlenk lines and gloveboxes.

The most common use of argon is likely the preservation of samples or presentation in element collections.

Handling

Safety

Argon is inert and will not react with any compounds, making it safe to use. It may pose an asphyxiation hazard in closed rooms. Since it's heavier than air, it will accumulate on the lower part of a room.

Storage

Compressed argon should be stored away from heat.

Disposal

Argon can be released in atmosphere, though best avoid closed spaces.

References

Relevant Sciencemadness threads

Retrieved from "https://www.sciencemadness.org/smwiki/index.php?title=Argon&oldid=7715"