Chemistry - Gold
Gold is a bright, reddish yellow, soft, dense, malleable, and ductile metal naturally found in the earth’s crust.
The symbol of gold is ‘Au’ and atomic number is ‘79.’
Gold is (chemically) a transition metal and belongs to group 11 of the periodic table.
Salient Features of Gold
Gold, which remains in a solid state under standard conditions, is the least reactive element.
Gold is resistant to most of the acids.
Gold does dissolve in aqua regia; aqua regia is a mixture of nitric acid and hydrochloric acid.
However, gold is insoluble in nitric acid.
Gold usually dissolves in alkaline solutions of cyanide.
Cyanide solutions are commonly used in mining and electroplating.
Gold also dissolves in mercury and forms ‘amalgam alloys.’
Gold does not react with oxygen at any temperature.
Occurrence of Gold
Gold commonly occurs as a free element i.e. in the natural form.
Gold occurs as nuggets or else found in in rocks, grains, in veins, and in some other alluvial deposits.
Gold also occurs in a solid solution forms with the native element such as silver (as electrum).
At some places, gold also naturally alloyed with copper and palladium.
Alloys of Gold
Following are the major alloys of gold −
Compounds of Gold
Following are the major compounds of the gold −
Gold (III) chloride - AuCl3
Gold (I) chloride - AuCl
Cyanide - CN
Chloroauric acid - HAuCl4
Gold (III) oxide - Au2O3
Gold bromide - AuBr
Aqua regia - HNO3+3HCl
Gold bromide - AuBr3
Gold (III) hydroxide - AuH3O3
Gold fluoride - AuF3
Gold (V) fluoride - AuF5
Gold sulfide - Au2S
Uses of Gold
Gold is one of the oldest elements that human being have been using for thousands of years.
As it is highly precious and provides a beautiful look, hence it is characteristically used in making ornaments.
As per the recent trend (of the world), about 50% gold is used in making jewelry, 40% used in investments, and remaining 10% is used in industry.