Difference between revisions of "Arsenic"

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[[File:Arsenic1.jpg|thumb|220x220px]]
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{{Infobox element
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'''Arsenic''' is a metalloid with the symbol '''As''' and atomic number 33. It appears in pure form as a shiny, metal-like substance, though most samples are gray due to oxidation. Aside from its once-popular use in poisoning, arsenic was also used for wood treatment chemicals.  
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<!-- General properties -->
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|name=Arsenic
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|symbol=As
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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=Grey (most common)<br>Yellow<br>Black
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|appearance=Metallic grey
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<!-- Periodic table -->
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|above=[[Phosphorus|P]]
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|below=[[Antimony|Sb]]
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|left=Germanium
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|right=Selenium
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|number=33
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|atomic mass=74.921595(6)
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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=15
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|group ref=
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|group comment=(pnictogens)
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|period=4
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|period ref=
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|period comment=
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|block=p
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|block ref=
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|block comment=
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|electron configuration=[Ar] 3d<sup>10</sup> 4s<sup>2</sup> 4p<sup>3</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, 5
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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-gray
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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=
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|melting point C=
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|melting point F=
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|melting point ref=
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|melting point comment=
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|boiling point K=
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|boiling point C=
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|boiling point F=
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|boiling point ref=
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|boiling point comment=
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|sublimation point K=887
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|sublimation point C=615
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|sublimation point F=1137
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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=5.727
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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 ref=
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|density gpcm3nrt 3=
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|density gpcm3nrt 3 comment=
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|density gpcm3mp=5.22
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|density gpcm3mp ref=
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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=1090
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|triple point kPa=3628
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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=1673
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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=24.44
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|heat fusion ref=
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|heat fusion comment= (gray)
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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=34.76
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|heat vaporization ref=
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|heat vaporization comment=
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|heat capacity=24.64
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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=553
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|vapor pressure 10=596
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|vapor pressure 100=646
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|vapor pressure 1 k=706
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|vapor pressure 10 k=781
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|vapor pressure 100 k=874
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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='''5''', 4, '''3''', 2, 1, −1, −2, '''−3'''
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|oxidation states ref=
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|oxidation states comment=
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|electronegativity=2.18
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|electronegativity ref=
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|electronegativity comment=
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|ionization energy 1=947
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|ionization energy 1 ref=
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|ionization energy 1 comment=
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|ionization energy 2=1798
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|ionization energy 2 ref=
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|ionization energy 2 comment=
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|ionization energy 3=2735
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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=119
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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=119±4
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|covalent radius ref=
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|covalent radius comment=
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|Van der Waals radius=185
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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=Rhombohedral
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|crystal structure prefix=
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|crystal structure ref=
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|crystal structure comment=
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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=
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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=
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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=5.6
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|thermal expansion ref=
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|thermal expansion comment= (at r.t.)
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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=50.2
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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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|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=333
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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=8
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|Young's modulus ref=
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|Young's modulus comment=
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|Shear modulus=
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|Shear modulus ref=
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|Shear modulus comment=
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|Bulk modulus=22
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|Bulk modulus ref=
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|Bulk modulus comment=
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|Poisson ratio=
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|Poisson ratio ref=
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|Poisson ratio comment=
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|Mohs hardness=3.5
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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=
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|Vickers hardness ref=
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|Vickers hardness comment=
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|Brinell hardness=1440
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|Brinell hardness ref=
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|Brinell hardness comment=
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|CAS number=7440-38-2
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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 ref=
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|prediction date=
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|discovered by=
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|discovery date ref=
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|discovery date= c. 800 CE
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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=
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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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'''Arsenic''' is a metalloid with the symbol '''As''' and atomic number 33. It appears in pure form as a shiny, metal-like substance, though most samples are dark grey due to oxidation. Aside from its once-popular use in poisoning, arsenic was also used for preparing wood treatment chemicals.  
  
 
==Properties==
 
==Properties==
 
===Chemical===
 
===Chemical===
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Arsenic has two important oxidation states, +3 and +5. Notable compounds are arsine (AsH<sub>3</sub>), arsenic trichloride (AsCl<sub>3</sub>, "butter of arsenic"), and the two oxides As<sub>4</sub>O<sub>6</sub> and As<sub>4</sub>O<sub>10</sub>.
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Arsenic has three important oxidation states, -3, +3 and +5. Notable compounds are arsine (AsH<sub>3</sub>), arsenic trichloride (AsCl<sub>3</sub>, "butter of arsenic"), and the two oxides As<sub>4</sub>O<sub>6</sub> and As<sub>4</sub>O<sub>10</sub>.
  
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Most of arsenic's compounds, as well as the element itself, are prone to sublimation at low temperatures (usually around 300 - 700 C).
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Most arsenic compounds, as well as the element itself, are prone to sublimation at low temperatures (usually around 300 - 700 °C).
  
 
=== Physical ===
 
=== Physical ===
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Arsenic occurs in three major [[Allotrope|allotropes]]: grey(or metallic), black, and yellow. Grey is by far the most commonly encountered form, and has semimetal properties. The yellow allotrope is encountered as a yellow amorphous solid, produced by very rapidly cooling arsenic vapor, and is not to be confused with orpiment, the sulfide mineral of arsenic. Yellow arsenic will slowly convert to grey over time. Black arsenic is brittle, glassy, and crystalline, forming from the cooling of arsenic vapor to more moderately high temperatures in the range of 100-200°C.
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Arsenic occurs in three major [[allotrope]]s: grey (or metallic), black, and yellow. The grey allotrope is by far the most commonly encountered form, and has semimetal properties. The yellow allotrope is encountered as a yellow amorphous solid, produced by very rapidly cooling arsenic vapor, and is not to be confused with orpiment, the sulfide mineral of arsenic. Yellow arsenic will slowly convert to the grey form over time. Black arsenic is brittle, glassy, and crystalline, forming from the cooling of arsenic vapor to more moderately high temperatures in the range of 100-200 °C.
  
 
Arsenic is unique among elements in that it typically does not occur in a liquid phase, but rather freely transfers between the solid and gas phases, often vaporizing even below its sublimation point, which only adds to the danger of this element.
 
Arsenic is unique among elements in that it typically does not occur in a liquid phase, but rather freely transfers between the solid and gas phases, often vaporizing even below its sublimation point, which only adds to the danger of this element.
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Certain mineral ores of arsenic can be found at rock and gem fairs, such as skutterudite (CoAs<sub>3</sub>) and arsenopyrite (FeAsS). It can also be bought online.
 
Certain mineral ores of arsenic can be found at rock and gem fairs, such as skutterudite (CoAs<sub>3</sub>) and arsenopyrite (FeAsS). It can also be bought online.
  
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In some places, the sell of arsenic and arsenic compounds is regulated.
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In some places, the sale of arsenic and arsenic compounds is regulated.
  
 
==Preparation/Isolation==
 
==Preparation/Isolation==
 
If you do not have any experience handling arsenic compounds, it is highly recommended you do not try to produce arsenic. Do not produce arsenic indoors without excellent ventilation. A glove box is also ideal.
 
If you do not have any experience handling arsenic compounds, it is highly recommended you do not try to produce arsenic. Do not produce arsenic indoors without excellent ventilation. A glove box is also ideal.
  
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Assuming that one has thoroughly researched the toxicity of arsenic and proper handling procedures from a reliable source, there are two major ways to prepare elemental arsenic. The first the wet method - involving dissolving the cation part of the ore (usually some metal) in nitric acid, leaving behind a residue of arsenic(III) oxide and reducing this to the metal.
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Assuming that one has thoroughly researched the toxicity of arsenic and proper handling procedures from a reliable source, there are two major ways to prepare elemental arsenic. The first the wet method - involving dissolving the cation part of the ore (usually some metal) in nitric acid, leaving behind a residue of arsenic(III) oxide and reducing this to the element.
  
 
The second, and by far the most lethal, is to sublimate the crushed ore in a closed tube. It is absolutely required to weld the ends of the tube shut to prevent vapor of arsenic or arsenic oxides from escaping, and one should probably add some reducing agent such as carbon as well to prevent the arsenic vapor reacting with the air in the closed container. When sublimating, heating should be done so that all of the vapor collects at one spot - this will make collection of the sublimated product significantly easier.
 
The second, and by far the most lethal, is to sublimate the crushed ore in a closed tube. It is absolutely required to weld the ends of the tube shut to prevent vapor of arsenic or arsenic oxides from escaping, and one should probably add some reducing agent such as carbon as well to prevent the arsenic vapor reacting with the air in the closed container. When sublimating, heating should be done so that all of the vapor collects at one spot - this will make collection of the sublimated product significantly easier.

Latest revision as of 15:37, 20 September 2018

Arsenic,  33As
Arsenic1.jpg
General properties
Name, symbol Arsenic, As
Allotropes Grey (most common)
Yellow
Black
Appearance Metallic grey
Arsenic in the periodic table
P
↑
As
↓
Sb
Germanium ← Arsenic → Selenium
Atomic number 33
Standard atomic weight (Ar) 74.921595(6)
Group, block (pnictogens); p-block
Period period 4
Electron configuration [Ar] 3d10 4s2 4p3
per shell
 2, 8, 18, 5
Physical properties
Silvery-gray
Phase Solid
Sublimation point 887 K ​(615 °C, ​1137 °F)
Density near r.t. 5.727 g/cm3
when liquid, at  5.22 g/cm3
Triple point 1090 K, ​3628 kPa
Critical point 1673 K,  MPa
Heat of fusion 24.44 kJ/mol (gray)
Heat of 34.76 kJ/mol
Molar heat capacity 24.64 J/(mol·K)
 pressure
Atomic properties
Oxidation states 5, 4, 3, 2, 1, −1, −2, −3
Electronegativity Pauling scale: 2.18
energies 1st: 947 kJ/mol
2nd: 1798 kJ/mol
3rd: 2735 kJ/mol
Atomic radius empirical: 119 pm
Covalent radius 119±4 pm
Van der Waals radius 185 pm
Miscellanea
Crystal structure ​
Thermal expansion 5.6 µm/(m·K) (at r.t.)
Thermal conductivity 50.2 W/(m·K)
Electrical resistivity 333 Ω·m (at 20 °C)
Magnetic ordering Diamagnetic
Young's modulus 8 GPa
Bulk modulus 22 GPa
Mohs hardness 3.5
Brinell hardness 1440 MPa
CAS Registry Number 7440-38-2
History
Discovery c. 800 CE
· references

Arsenic is a metalloid with the symbol As and atomic number 33. It appears in pure form as a shiny, metal-like substance, though most samples are dark grey due to oxidation. Aside from its once-popular use in poisoning, arsenic was also used for preparing wood treatment chemicals.

Properties

Chemical

Arsenic has three important oxidation states, -3, +3 and +5. Notable compounds are arsine (AsH3), arsenic trichloride (AsCl3, "butter of arsenic"), and the two oxides As4O6 and As4O10.

Most arsenic compounds, as well as the element itself, are prone to sublimation at low temperatures (usually around 300 - 700 °C).

Physical

Arsenic occurs in three major allotropes: grey (or metallic), black, and yellow. The grey allotrope is by far the most commonly encountered form, and has semimetal properties. The yellow allotrope is encountered as a yellow amorphous solid, produced by very rapidly cooling arsenic vapor, and is not to be confused with orpiment, the sulfide mineral of arsenic. Yellow arsenic will slowly convert to the grey form over time. Black arsenic is brittle, glassy, and crystalline, forming from the cooling of arsenic vapor to more moderately high temperatures in the range of 100-200 °C.

Arsenic is unique among elements in that it typically does not occur in a liquid phase, but rather freely transfers between the solid and gas phases, often vaporizing even below its sublimation point, which only adds to the danger of this element.

Availability

Certain mineral ores of arsenic can be found at rock and gem fairs, such as skutterudite (CoAs3) and arsenopyrite (FeAsS). It can also be bought online.

In some places, the sale of arsenic and arsenic compounds is regulated.

Preparation/Isolation

If you do not have any experience handling arsenic compounds, it is highly recommended you do not try to produce arsenic. Do not produce arsenic indoors without excellent ventilation. A glove box is also ideal.

Assuming that one has thoroughly researched the toxicity of arsenic and proper handling procedures from a reliable source, there are two major ways to prepare elemental arsenic. The first the wet method - involving dissolving the cation part of the ore (usually some metal) in nitric acid, leaving behind a residue of arsenic(III) oxide and reducing this to the element.

The second, and by far the most lethal, is to sublimate the crushed ore in a closed tube. It is absolutely required to weld the ends of the tube shut to prevent vapor of arsenic or arsenic oxides from escaping, and one should probably add some reducing agent such as carbon as well to prevent the arsenic vapor reacting with the air in the closed container. When sublimating, heating should be done so that all of the vapor collects at one spot - this will make collection of the sublimated product significantly easier.

Projects

Handling

Safety

Arsenic is notoriously one of the most toxic elements on the periodic table, as less than half a gram will cause death in a very painful fashion. When working with this, gloves, a lab coat, full facial protection, and a fume hood are a must. If volatilized and organic arsenic compounds are used, a glove box or gas mask is not optional - you must use one if you plan to live afterwards.

Toxicity of arsenic-bearing ores

The only arsenic ore that can be considered almost non-toxic (safe enough to handle by hand in powdered form) is skutterudite, due to its crystal structure effectively trapping the arsenic atoms in a lattice of cobalt, iron and sometimes nickel. Other ores such as arsenopyrite, realgar and orpiment are safe to handle by hand in bulk form, but not under any other conditions (and it's frankly recommended to not handle any of these by hand anyway).

Storage

Arsenic should be stored in closed bottles or ampoules.

Disposal

NEVER DUMP ARSENIC IN THE ENVIRONMENT! All arsenic compounds must be taken to hazardous chemicals disposal centers.

The only exception would be to redeposit it in the geological area from where you collected the arsenic containing mineral, as there is already arsenic in that area. Even so, the arsenic must be converted to an inert compound, to prevent it from infiltrating the groundwater.

References

Sciencemadness Library

Relevant Sciencemadness threads

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