Post on 24-Dec-2015
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 grinding2) Froth flotation3) Roasting4) a) pyrometallurgy
b) electrowinning5) Electrolysis of molten ore
Application: anti-corrosion
Cathodic Cathodic protectionprotection
◆ 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 Sacrificial protectionprotection
◆ Galvanization: Zn coating on Fe ◇ Zn is more reactive than Fe◆ Zn releases electron to Fe◇ Zn is corroded first to save Fe evenwhen the Zn coating is scratched
Application: alloy
BrassBrass
◆ Cu + Zn◇ low melting point: 900-940oC◆ more ductile / stronger than Cu alone◇ has superior corrosion resistance
Cadmium Cadmium zinc zinc
telluridetelluride
◆ Cadmium telluride + zinc telluride◇ Direct bandgap semiconductor
Application: use of other compounds
Zinc oxideZinc oxide ◆ used as a white pigment in paints◇ protect its polymers from UV, thus often used in photocopying products
Zinc chlorideZinc chloride◆ deodorant ◇ often added to lumber as a fire retardant as a wood preservative
Zinc sulphideZinc sulphide◆ used in luminescent pigments (eg in X-ray / television screens)
Zinc lactateZinc lactate◇ 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
◆ 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 endThe end
Biological importance