Zinc
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  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
Cathodic
protection
◆Zn: an efficient sacrificial anode in
cathodic 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
Brass
Cadmium
zinc
telluride
◆Cu + Zn
◇low melting point: 900-940oC
◆more ductile / stronger than
Cu alone
◇has superior corrosion
resistance
◆Cadmium telluride
+ zinc telluride
◇Direct bandgap
semiconductor
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
Zinc sulphide
Zinc lactate
◇ often added to lumber as a fire
retardant as a wood preservative
◆ used in luminescent pigments (eg
in X-ray / television screens)
◇ used in toothpaste in order to
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
 proteins use Zn to shift
conformations
 perform biological reactions
◇Zn deficiency
 growth retardation /
diarrhea, etc.
◆Zn overdose
 suppress Cu / Fe absorption
 ataxia / lethargy
The end