Difference between revisions of "Copper"

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[[File:Piece_of_copper.jpg|thumb|300px|A piece of copper, showing some minor oxidation]]
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{{Infobox element
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'''Copper''' is a transition metal with the symbol Cu and the atomic number 29. It is a widely available commodity and can be obtained in numerous forms. It is an amphoteric metal that exists in two common oxidation states, +1 and +2, and can also exist in a +3 and a +4 state. Copper itself is chemically resistant, but its oxidation states show tendencies to react. It can be plated out of solution or replaced by a more active metal.
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<!-- top -->
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|image name=Electrolytic copper.jpg
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|image alt=
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|image size=300
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|image name comment=Dendritic copper crystals made by electrolysis.
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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=Copper
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|symbol=Cu
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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= Reddish metallic
 +
<!-- Periodic table -->
 +
|above=
 +
|below=[[Silver]]
 +
|left=[[Nickel]]
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|right=[[Zinc]]
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|number=29
 +
|atomic mass=63.546(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=
 +
|group=11
 +
|group ref=
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|group comment=
 +
|period=4
 +
|period ref=
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|period comment=
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|block=d
 +
|block ref=
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|block comment=
 +
|electron configuration=[Ar] 3d<sup>10</sup> 4s<sup>1</sup>
 +
|electron configuration ref=
 +
|electron configuration comment=
 +
|electrons per shell=2, 8, 18, 1
 +
|electrons per shell ref=
 +
|electrons per shell comment=
 +
<!-- Physical properties -->
 +
|physical properties comment=
 +
|color=Reddish metallic
 +
|phase=Solid
 +
|phase ref=
 +
|phase comment=
 +
|melting point K=1357.77
 +
|melting point C=1084.62
 +
|melting point F=1984.32
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|melting point ref=
 +
|melting point comment=
 +
|boiling point K=2835
 +
|boiling point C=2562
 +
|boiling point F=​4643
 +
|boiling point ref=
 +
|boiling point comment=
 +
|sublimation point K=
 +
|sublimation point C=
 +
|sublimation point F=
 +
|sublimation point ref=
 +
|sublimation point comment=
 +
|density gplstp=
 +
|density gplstp ref=
 +
|density gplstp comment=
 +
|density gpcm3nrt=8.96
 +
|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 2 comment=
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|density gpcm3nrt 3=
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|density gpcm3nrt 3 ref=
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|density gpcm3nrt 3 comment=
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|density gpcm3mp=8.02
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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=
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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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|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=
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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=13.26
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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=300.4
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|heat vaporization ref=
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|heat vaporization comment=
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|heat capacity=24.44
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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=1509
 +
|vapor pressure 10=1661
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|vapor pressure 100=1850
 +
|vapor pressure 1 k=2089
 +
|vapor pressure 10 k=2404
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|vapor pressure 100 k=2834
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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=−2, +1, '''+2''', +3, +4
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|oxidation states ref=
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|oxidation states comment=​(a mildly basic oxide)
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|electronegativity=1.90
 +
|electronegativity ref=
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|electronegativity comment=
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|ionization energy 1=745.5
 +
|ionization energy 1 ref=
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|ionization energy 1 comment=
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|ionization energy 2=1957.9
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|ionization energy 2 ref=
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|ionization energy 2 comment=
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|ionization energy 3=3555
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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=128
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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=132±4
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|covalent radius ref=
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|covalent radius comment=
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|Van der Waals radius=140
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|Van der Waals radius ref=
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|Van der Waals radius comment=
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<!-- Miscellanea -->
 +
|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)
 +
|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.=3810
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|speed of sound rod at r.t. ref=
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|speed of sound rod at r.t. comment=(annealed)
 +
|thermal expansion=
 +
|thermal expansion ref=
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|thermal expansion comment=
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|thermal expansion at 25=16.5
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|thermal expansion at 25 ref=
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|thermal expansion at 25 comment=
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|thermal conductivity=401
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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 ref=
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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=16.78·10<sup>-9</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=Diamagnetic
 +
|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=110–128
 +
|Young's modulus ref=
 +
|Young's modulus comment=
 +
|Shear modulus=48
 +
|Shear modulus ref=
 +
|Shear modulus comment=
 +
|Bulk modulus=140
 +
|Bulk modulus ref=
 +
|Bulk modulus comment=
 +
|Poisson ratio=0.34
 +
|Poisson ratio ref=
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|Poisson ratio comment=
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|Mohs hardness=3.0
 +
|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=
 +
|Vickers hardness=343–369
 +
|Vickers hardness ref=
 +
|Vickers hardness comment=
 +
|Brinell hardness=235–878
 +
|Brinell hardness ref=
 +
|Brinell hardness comment=
 +
|CAS number=7440-50-8
 +
|CAS number ref=
 +
|CAS number comment=
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<!-- History -->
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|naming=After Cyprus, principal mining place in Roman era (Cyprium)
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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=
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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 ref=
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|named date=
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|history comment label=
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|history comment= Middle East (9000 BC)
 +
<!-- Isotopes -->
 +
|isotopes=
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|isotopes comment=
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|engvar=
 +
}}
 +
'''Copper''' is a transition metal with the symbol '''Cu''' and the atomic number 29. It is a widely available commodity and can be obtained in numerous forms. It is an amphoteric metal that exists in two common oxidation states, +1 and +2, and can also exist in a +3 and a +4 state. Copper itself is chemically resistant, but its oxidation states show tendencies to react. It can be plated out of solution or replaced by a more active metal.
  
 
==Properties==
 
==Properties==
 
===Physical properties===
 
===Physical properties===
−
Copper is a reddish metal that is highly malleable and ductile. It can take a high polish, but often appears dull. Older pieces may be coated with the black [[copper(II) oxide]]. It has extremely high conductance of both heat and electricity.
+
Copper is a reddish-pink metal that is highly malleable and ductile. It can take a high polish, but often appears dull. Older pieces may be coated with the black [[copper(II) oxide]]. It has extremely high conductance of both heat and electricity.
 +
 
 +
The softness of copper partly explains its high electrical conductivity (59.6×10<sup>6</sup> S/m) and high thermal conductivity, second highest among pure metals at room temperature (after [[silver]]). This is because the resistivity to electron transport in metals at room temperature originates primarily from scattering of electrons on thermal vibrations of the lattice, which are relatively weak in a soft metal. However, this is only true for a few soft metals.
  
 
===Chemical properties===
 
===Chemical properties===
−
Copper is notable for its varied chemistry. Copper metal will not dissolve in strong acids, but the addition of an oxidizer such as [[hydrogen peroxide]] permits the dissolution of the metal in most acids. N[[File:Copper_compounds.jpg|thumb|256px|Two copper compounds, tetraamminecopper(II) sulfate and tetrachlorocupric acid.]]itric acid is a sufficiently strong oxidizer to dissolve copper metal. In both cases copper will exist in the +2 (cupric) state, the most common for copper. Compounds of copper(II) are generally bluish.
+
Copper is notable for its varied chemistry. Copper metal will not dissolve in strong acids, but the addition of an oxidizer such as [[hydrogen peroxide]] permits the dissolution of the metal in most acids. Nitric acid is a sufficiently strong oxidizer to dissolve copper metal.
 +
 
 +
: 3 Cu + 8 HNO<sub>3</sub> → 3 Cu(NO<sub>3</sub>)<sub>2</sub> + 2 NO + 4 H<sub>2</sub>O
 +
 
 +
The nitric oxide produced may react with atmospheric oxygen to give nitrogen dioxide. With more concentrated nitric acid, nitrogen dioxide is produced directly in a reaction with 1:4 stoichiometry:
 +
 
 +
: Cu + 4 HNO<sub>3</sub> → Cu(NO<sub>3</sub>)<sub>2</sub> + 2 NO<sub>2</sub> + 2 H<sub>2</sub>O
 +
 
 +
In both cases copper will exist in the +2 (cupric) state, the most common for copper. Compounds of copper(II) are generally blue or green in color.
 +
 
 +
When a sufficiently strong reducer, such as iodide, [[ascorbic acid]] or [[glucose]], is used to oxidize copper 2+, it may enter the +1 (cuprous) state.
 +
 
 +
: Cu<sup>2+</sup> → Cu<sup>+</sup>
 +
 
 +
Addition of hydrochloric acid to copper(I) oxide forms copper(I) chloride:
 +
 
 +
: Cu<sub>2</sub>O + 2 HCl → 2 CuCl + H<sub>2</sub>O
 +
 
 +
If excess HCl is added, a stable, soluble copper(I) complex is formed:
 +
 
 +
: CuCl + Cl<sup>-</sup> → [CuCl<sub>2</sub>]<sup>-</sup>
 +
 
 +
Copper(I) compounds are generally insoluble in water and highly reducing. Most of them are white, though [[copper(I) chloride]] may vary in color due to various impurities, and [[copper(I) oxide]] is red, or yellow when prepared by certain routes.
  
−
When a sufficiently strong reducer, such as iodide or ascorbic acid, is used to oxidize copper, it may enter the +1 (cuprous) state. Copper(I) compounds are generally insoluble in water and highly reducing. Most of them are white, though [[copper(I) chloride]] may vary in color due to various impurities, and [[copper(I) oxide]] is red, or yellow when prepared by certain routes.
+
Copper also has extensive coordination chemistry in both the +1 and +2 states. While copper(I) compounds are insoluble in water, the proper ligand, such as [[ammonia]], [[cyanide]], [[thiosulfate]], or chloride, the copper(I) ion becomes soluble in water. Copper(II) compounds undergo dramatic color changes with the addition of proper ligands: with chloride, a green complex forms (though a red complex, trichlorocuprate, is known to exist); with ammonia and [[ethylenediamine]], a dark blue complex forms, with bromide, a maroon complex forms, and with [[ascorbic acid]], a yellow complex forms.
−
[[File:Copper flame.JPG|thumb|220x220px|Copper(II) ions turn an ordinary flame blue or green.]]
+
−
Copper also has extensive coordination chemistry in both the +1 and +2 states. While copper(I) compounds are insoluble in water, the proper ligand, such as [[ammonia]], [[cyanide]], [[thiosulfate]], or [[chloride]], the copper(I) ion becomes soluble in water. Copper(II) compounds undergo dramatic color changes with the addition of proper ligands: with chloride, a green complex forms (though a red complex, trichlorocuprate, is known to exist); with ammonia and [[ethylenediamine]], a dark blue complex forms, with [[bromide]], a maroon complex forms, and with [[ascorbic acid]], a yellow complex forms.
+
  
 
Copper(III) compounds can be made in the amateur chemist's lab with [[sodium persulfate]] and [[potassium periodate]].
 
Copper(III) compounds can be made in the amateur chemist's lab with [[sodium persulfate]] and [[potassium periodate]].
  
−
One copper(IV) compound is known to exist, but is inaccessible to the amateur due to the requirement of fluorine gas.
+
One copper(IV) compound is known to exist, but is inaccessible to the amateur due to the requirement of [[fluorine]] gas.
  
 
==Availability==
 
==Availability==
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Under certain circumstances, a copper foil may be produced instead of powder, usually if [[copper(II) chloride]] is used, in an acidic solution.
 
Under certain circumstances, a copper foil may be produced instead of powder, usually if [[copper(II) chloride]] is used, in an acidic solution.
  
−
Clean, superfine, and air-stable copper powder can be created by adding [[ascorbic acid]](vitamin C) to a solution of copper sulfate followed by boiling for a time. An excess of ascorbic acid yields the copper powder and a yellow solution; the composition of this solution has yet to be determined.<ref>Experiment performed 6/17/14 by No Tears Only Dreams Now</ref>
+
Clean, superfine, and air-stable copper powder can be created by adding [[ascorbic acid]] (vitamin C) to a solution of copper sulfate followed by boiling for a time. An excess of ascorbic acid yields the copper powder and a yellow solution; the composition of this solution has yet to be determined.<ref>Experiment performed 6/17/14 by No Tears Only Dreams Now</ref>
  
 
==Projects==
 
==Projects==
 +
*Make copper(II) oxide
 +
*Make [[copper(II) sulfate]]
 
*Illustrations of [[Le Chatelier's principle]]
 
*Illustrations of [[Le Chatelier's principle]]
−
*[[Growing crystals]]
+
*[[Crystal growing|Growing crystals]]
 
*Copper [[soap]]
 
*Copper [[soap]]
−
*[[Alloys of copper|Copper alloys]]
+
*Make copper alloys ([[brass]], [[bronze]])
 +
*Cast beautiful copper metal items
  
 
==Handling==
 
==Handling==
 
===Safety===
 
===Safety===
−
Copper metal poses little toxicity and clean copper metals are known to have antiseptic properties, thought not as powerful as [[silver]].
+
Copper metal poses little toxicity and clean copper metal items are known to have antiseptic properties, thought not as powerful as [[silver]]. As such, getting scratch by a fresh cut copper wire is less hazardous that if it was some other metal.
  
−
Copper compounds are moderately toxic. They are irritant on contact with the eyes, mucous or inhaled.
+
Copper compounds also have antibiotic properties, being used as preservatives in sample analysis and biology. They are however moderately toxic, and excess intake of copper is harmful. They are also irritant on contact with the eyes, mucous or inhaled. Contact with the bare skin may reduce copper compounds to copper oxide or some other insoluble copper compounds, which will slightly stain the skin. Copper halides or oxohalides will visibly stain the skin.
  
 
===Storage===
 
===Storage===
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Special disposal procedures are required with copper compounds. All copper waste should be converted to the +2 state with peroxide and converted to the carbonate. This waste should never be dumped down the drain: rather it should be taken to the proper disposal facility or recycled.
 
Special disposal procedures are required with copper compounds. All copper waste should be converted to the +2 state with peroxide and converted to the carbonate. This waste should never be dumped down the drain: rather it should be taken to the proper disposal facility or recycled.
  
−
Recycling copper back to metallic form is easy: dissolve the copper(II) carbonate in a suitable acid, such as sulfuric acid, and then add in a reducing agent. Iron, zinc or aluminium are a good choice as they're cheap and available in large quantities. If [[aluminium|aluminum]] is used, a chloride source should be added to promote replacement and break the protective [[aluminium oxide|Al<sub>2</sub>O<sub>3</sub>]]<sub> </sub>layer.
+
Recycling copper back to metallic form is very easy: dissolve the copper(II) carbonate in a suitable acid, such as [[sulfuric acid]], and then add in a reducing agent. [[Iron]], [[zinc]] or [[aluminium]] are a good choice as they're cheap and available in large quantities. If [[aluminium]] is used, a chloride source should be added to promote replacement and break the protective [[aluminium oxide|Al<sub>2</sub>O<sub>3</sub>]] layer.
 +
 
 +
==Gallery==
 +
<gallery widths="200" position="center" columns="4" orientation="none">
 +
Copper bullion 3N.jpg|28 gram 3N copper bar
 +
Piece of copper by Zts16.jpg|A piece of copper, showing some minor oxidation
 +
Pouring molten copper metal in ingot mold by Tito4re.png|Molten copper being poured in an ingot mold
 +
Copper flame.jpg|Copper(II) ions turn an ordinary flame blue or green
 +
Copper compounds by Brain&Force.jpg|Two copper compounds, tetraamminecopper(II) sulfate and tetrachlorocupric acid
 +
Cupric_oxide.JPG|Copper(II) oxide, copper compound showing a different color than the usual blue or green
 +
</gallery>
  
 
==See also==
 
==See also==
−
*[http://sciencemadness.wikia.com/wiki/Category:Copper_compounds Copper compounds]
+
*[[:Category:Copper_compounds|Copper compounds]]
 +
*[[Brass]]
 +
*[[Bronze]]
 +
*[[Devarda's alloy]]
  
 
==References==
 
==References==
 
<references />
 
<references />
 
===Relevant Sciencemadness threads===
 
===Relevant Sciencemadness threads===
−
[[Category:Metals]]
+
*[http://www.sciencemadness.org/talk/viewthread.php?tid=23967 Pyrophoric copper: How?]
 +
*[http://www.sciencemadness.org/talk/viewthread.php?tid=2654 Precipitated copper powder]
 +
*[http://www.sciencemadness.org/talk/viewthread.php?tid=64308 Copper Thermite]
 +
*[http://www.sciencemadness.org/talk/viewthread.php?tid=62936 500 ml copper flask]
 +
*[http://www.sciencemadness.org/talk/viewthread.php?tid=13377 removing trace copper impurities from AgNO3]
 +
*[http://www.sciencemadness.org/talk/viewthread.php?tid=3611 Copper plating isn't going too well]
 +
*[http://www.sciencemadness.org/talk/viewthread.php?tid=24547 Copper electroplating non-conductive material with PC power supply?]
 +
*[http://www.sciencemadness.org/talk/viewthread.php?tid=14093 Electroforming Copper Liners]
 +
*[http://www.sciencemadness.org/talk/viewthread.php?tid=22957 Electrolysis of Copper Sulfate (Electrodes)]
 +
*[http://www.sciencemadness.org/talk/viewthread.php?tid=25430 Copper Cathode Electrolysis]
 +
*[https://www.sciencemadness.org/whisper/viewthread.php?tid=28779 copper bar stock]
 +
*[http://www.sciencemadness.org/talk/viewthread.php?tid=73819 Finding copper in common items?]
 +
 
 
[[Category:Elements]]
 
[[Category:Elements]]
−
[[Category:Readily available chemicals]]
+
[[Category:Metals]]
 
[[Category:Transition metals]]
 
[[Category:Transition metals]]
 +
[[Category:Readily available chemicals]]
 
[[Category:Materials isolable by electrowinning]]
 
[[Category:Materials isolable by electrowinning]]
 
[[Category:D-block]]
 
[[Category:D-block]]
 
[[Category:Essential reagents]]
 
[[Category:Essential reagents]]
 +
[[Category:Noble metals]]
 +
[[Category:Minerals]]
 +
[[Category:Coinage metals]]

Latest revision as of 12:11, 25 June 2023

Copper,  29Cu
Electrolytic copper.jpg
Dendritic copper crystals made by electrolysis.
General properties
Name, symbol Copper, Cu
Appearance Reddish metallic
Copper in the periodic table

↑
Cu
↓
Silver
Nickel ← Copper → Zinc
Atomic number 29
Standard atomic weight (Ar) 63.546(3)
Group, block , d-block
Period period 4
Electron configuration [Ar] 3d10 4s1
per shell
 2, 8, 18, 1
Physical properties
Reddish metallic
Phase Solid
Melting point 1357.77 K ​(1084.62 °C, ​1984.32 °F)
Boiling point 2835 K ​(2562 °C, ​​4643 °F)
Density near r.t. 8.96 g/cm3
when liquid, at  8.02 g/cm3
Heat of fusion 13.26 kJ/mol
Heat of 300.4 kJ/mol
Molar heat capacity 24.44 J/(mol·K)
 pressure
Atomic properties
Oxidation states −2, +1, +2, +3, +4 ​​(a mildly basic oxide)
Electronegativity Pauling scale: 1.90
energies 1st: 745.5 kJ/mol
2nd: 1957.9 kJ/mol
3rd: 3555 kJ/mol
Atomic radius empirical: 128 pm
Covalent radius 132±4 pm
Van der Waals radius 140 pm
Miscellanea
Crystal structure ​Face-centered cubic (fcc)
Speed of sound thin rod 3810 m/s (at ) (annealed)
Thermal expansion 16.5 µm/(m·K) (at 25 °C)
Thermal conductivity 401 W/(m·K)
Electrical resistivity 16.78·10-9 Ω·m (at 20 °C)
Magnetic ordering Diamagnetic
Young's modulus 110–128 GPa
Shear modulus 48 GPa
Bulk modulus 140 GPa
Poisson ratio 0.34
Mohs hardness 3.0
Vickers hardness 343–369 MPa
Brinell hardness 235–878 MPa
CAS Registry Number 7440-50-8
History
Naming After Cyprus, principal mining place in Roman era (Cyprium)
Middle East (9000 BC)
· references

Copper is a transition metal with the symbol Cu and the atomic number 29. It is a widely available commodity and can be obtained in numerous forms. It is an amphoteric metal that exists in two common oxidation states, +1 and +2, and can also exist in a +3 and a +4 state. Copper itself is chemically resistant, but its oxidation states show tendencies to react. It can be plated out of solution or replaced by a more active metal.

Properties

Physical properties

Copper is a reddish-pink metal that is highly malleable and ductile. It can take a high polish, but often appears dull. Older pieces may be coated with the black copper(II) oxide. It has extremely high conductance of both heat and electricity.

The softness of copper partly explains its high electrical conductivity (59.6×106 S/m) and high thermal conductivity, second highest among pure metals at room temperature (after silver). This is because the resistivity to electron transport in metals at room temperature originates primarily from scattering of electrons on thermal vibrations of the lattice, which are relatively weak in a soft metal. However, this is only true for a few soft metals.

Chemical properties

Copper is notable for its varied chemistry. Copper metal will not dissolve in strong acids, but the addition of an oxidizer such as hydrogen peroxide permits the dissolution of the metal in most acids. Nitric acid is a sufficiently strong oxidizer to dissolve copper metal.

3 Cu + 8 HNO3 → 3 Cu(NO3)2 + 2 NO + 4 H2O

The nitric oxide produced may react with atmospheric oxygen to give nitrogen dioxide. With more concentrated nitric acid, nitrogen dioxide is produced directly in a reaction with 1:4 stoichiometry:

Cu + 4 HNO3 → Cu(NO3)2 + 2 NO2 + 2 H2O

In both cases copper will exist in the +2 (cupric) state, the most common for copper. Compounds of copper(II) are generally blue or green in color.

When a sufficiently strong reducer, such as iodide, ascorbic acid or glucose, is used to oxidize copper 2+, it may enter the +1 (cuprous) state.

Cu2+ → Cu+

Addition of hydrochloric acid to copper(I) oxide forms copper(I) chloride:

Cu2O + 2 HCl → 2 CuCl + H2O

If excess HCl is added, a stable, soluble copper(I) complex is formed:

CuCl + Cl- → [CuCl2]-

Copper(I) compounds are generally insoluble in water and highly reducing. Most of them are white, though copper(I) chloride may vary in color due to various impurities, and copper(I) oxide is red, or yellow when prepared by certain routes.

Copper also has extensive coordination chemistry in both the +1 and +2 states. While copper(I) compounds are insoluble in water, the proper ligand, such as ammonia, cyanide, thiosulfate, or chloride, the copper(I) ion becomes soluble in water. Copper(II) compounds undergo dramatic color changes with the addition of proper ligands: with chloride, a green complex forms (though a red complex, trichlorocuprate, is known to exist); with ammonia and ethylenediamine, a dark blue complex forms, with bromide, a maroon complex forms, and with ascorbic acid, a yellow complex forms.

Copper(III) compounds can be made in the amateur chemist's lab with sodium persulfate and potassium periodate.

One copper(IV) compound is known to exist, but is inaccessible to the amateur due to the requirement of fluorine gas.

Availability

Copper is a common coinage material, and can be found in United States pennies made before 1983. These are an alloy of 95% copper and 5% tin.

Several types of wiring contain copper metal. These wires may be glazed and will require removal before use.

Many electronics contain copper, such as transistors (the back metal plate that is in contact with the heat sink or covered by the plastic case), diodes (the wire), pins (though most are brass), rectifiers, PCBs, computer chips, on rare occasions some heat sinks are made of copper (or brass) etc. Some transistor heat sinks sometimes have an extra copper plate, for better heat dispersion.

Preparation

Copper metal powder can be made from copper(II) sulfate, available as root killer for septic systems, with the addition of either zinc metal or aluminium metal and a chloride source (such as table salt).

Copper powder can be made by reducing a copper salt, such as copper sulfate with iron. If impure iron, such as steel is used, the carbon from the steel will contaminate the solution and may slightly passivate the metal. However the black powder also contains copper(II) oxide, which too is black. The copper powder will require washing, though a simple decantation will suffice, as copper is denser than both contaminants.

Under certain circumstances, a copper foil may be produced instead of powder, usually if copper(II) chloride is used, in an acidic solution.

Clean, superfine, and air-stable copper powder can be created by adding ascorbic acid (vitamin C) to a solution of copper sulfate followed by boiling for a time. An excess of ascorbic acid yields the copper powder and a yellow solution; the composition of this solution has yet to be determined.[1]

Projects

Handling

Safety

Copper metal poses little toxicity and clean copper metal items are known to have antiseptic properties, thought not as powerful as silver. As such, getting scratch by a fresh cut copper wire is less hazardous that if it was some other metal.

Copper compounds also have antibiotic properties, being used as preservatives in sample analysis and biology. They are however moderately toxic, and excess intake of copper is harmful. They are also irritant on contact with the eyes, mucous or inhaled. Contact with the bare skin may reduce copper compounds to copper oxide or some other insoluble copper compounds, which will slightly stain the skin. Copper halides or oxohalides will visibly stain the skin.

Storage

Copper metal will develop a thin layer of oxide on its surface, that is usually not a problem and can be easily removed. However, if the copper metal was cleaned with acid before and hasn't been thoroughly washed, there is a risk of forming a patina. Copper powder is more sensitive and in moist air will rapidly oxidize to CuO. It is best stored in closed containers, either in inert gas (CO2 is enough) or under water or any other solvent. In case of the latter, there is the problem when drying the powder, as it may oxidize if done at a temperature too high in open air.

Hygroscopic copper compounds should be stored in sealed containers, to prevent them from absorbing the water from air.

Disposal

Special disposal procedures are required with copper compounds. All copper waste should be converted to the +2 state with peroxide and converted to the carbonate. This waste should never be dumped down the drain: rather it should be taken to the proper disposal facility or recycled.

Recycling copper back to metallic form is very easy: dissolve the copper(II) carbonate in a suitable acid, such as sulfuric acid, and then add in a reducing agent. Iron, zinc or aluminium are a good choice as they're cheap and available in large quantities. If aluminium is used, a chloride source should be added to promote replacement and break the protective Al2O3 layer.

Gallery

  • 28 gram 3N copper bar

  • A piece of copper, showing some minor oxidation

  • Molten copper being poured in an ingot mold

  • Copper(II) ions turn an ordinary flame blue or green

  • Two copper compounds, tetraamminecopper(II) sulfate and tetrachlorocupric acid

  • Copper(II) oxide, copper compound showing a different color than the usual blue or green

See also

References

  1. ↑ Experiment performed 6/17/14 by No Tears Only Dreams Now

Relevant Sciencemadness threads

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