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									Z in c   鋅
Basic info.
◆Symbol: Zn
◇Atomic no.: 30
◆Has 5 stable isotopes
 (64, 66, 67, 68, 70 Zn)
◇24th most abundant element in Earth’s crust
◆Large deposits in Australia, Canada, the US
 (with largest reserve in Iran)
◇The Earth has been estimated to have 46
 years supply of Zn
Discovery
◆Who: Andreas Marggraf
◇Nationality: German
◆When to discover: 1764
◇How: heat a mixture of calamine and carbon
 in a closed vessel à isolate zinc
Physical property
         ◆Lustrous solid at room temp.
         ◇Hard/Brittle at most temp.
         ◆Malleable between 100-150oC
         ◇Density: 7.14g/cm3
         ◆Boiling point: 907oC
         ◇Melting point: 419.53oC
         ◆Crystal structure: hexagonal
         ◇Fair conductor of electricity
Production
◆~70% Zn comes from mining
   (most from sphalerite, ZnS deposits)
◇~30% Zn comes from recycling of secondary Zn
◆Production process:
1) Ore grinding
2) Froth flotation
3) Roasting
4) a) pyrometallurgy
   b) electrowinning
5) Electrolysis of molten ore
Application: anti-corrosion
           ◆Zn: an efficient sacrificial anode in
Cathodic cathodic protection
protection ◇ Cathode of a car battery is always
           connected to the car body, supplying
           electrons to iron body


Sacrificial ◆ Galvanization: Zn coating on Fe
protection ◇ Zn is more reactive than Fe
            ◆ Zn releases electron to Fe
            ◇ Zn is corroded first to save Fe even
            when the Zn coating is scratched
Application: alloy
            ◆Cu + Zn
            ◇low melting point: 900-940oC
 Brass      ◆more ductile / stronger than
             Cu alone
            ◇has superior corrosion
             resistance

            ◆Cadmium telluride
             + zinc telluride
Cadmium
   zinc     ◇Direct bandgap
             semiconductor
telluride
Application: use of other compounds
   Zinc oxide     ◆ used as a white pigment in paints
                  ◇ protect its polymers from UV, thus
                  often used in photocopying products



                  ◆ deodorant
  Zinc chloride   ◇ often added to lumber as a fire
                  retardant as a wood preservative
                  ◆ used in luminescent pigments (eg
 Zinc sulphide    in X-ray / television screens)

                  ◇ used in toothpaste in order to
  Zinc lactate    prevent halitosis
Biological importance


◆Zn: essential trace
 element for human
◇Red meat :
 rich in Zn in general
◆Some plants
 (eg nuts) contain Zn
◇Highest conc. of Zn in body:
 in part of the eye / prostate
Biological importance
             ◆Zn: flexible coordinate
              geometry
              à proteins use Zn to shift
              conformations
              à perform biological reactions
             ◇Zn deficiency
              à growth retardation /
              diarrhea, etc.
             ◆Zn overdose
              à suppress Cu / Fe absorption
              à ataxia / lethargy
                                  The end

								
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