Chemistry - Gold


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Introduction

  • 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
  • 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 −

    • Colored gold

    • Crown gold

    • Electrum

    • Rose gold

    • Tumbaga

    • White 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

    • Fulminating gold

    • Gold salts

    • Gold heptafluoride

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.



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