What is Gold? | Element data, Properties and Uses

What is Gold?

Gold is a chemical element and its appearance is lustrous yellow metal. The symbol of gold is Au which is derived from the Latin word Aurum. Gold's atomic number is 79 and its atomic weight is 196.9. Gold is one of the higher atomic number elements that occur naturally. Gold is classified in the d-block elements, the 11th group, and the 6th period of the periodic table.  Its electronic configuration is [Xe] 4f 14 5d 10 6s 1. Gold has only one stable isotope which is naturally occurring. Its oxidation state ranges from +1 to +5, but Au (+1) and Au (+3) are dominant.

Occurrence

Gold is found mostly in the free state of quartz veins. Sometimes it is also alloyed with silver, platinum, and iron or bismuth as impurities. It's also found in the sands of the river which pass through any auriferous rocks and is found as telluride in sylvanite. It is also found in seawater but a few grams of gold in tons and tons of seawater. 

Extraction of gold

Extraction from Alluvial sand:

As gold has a high specific gravity, the gold-bearing sand is agitated with water by giving rotatory motion, the heavier gold particles settle down and the sand is washed away with water.

Extraction from Auriferous Quartz:

The pieces of the ore are crushed, broken into small pieces, and powdered, this powdered ore is washed and treated by any of the following two processes. 

• Amalgamation process

In this process, the gold paste is passed over amalgamated copper plates. The gold combines with mercury and forms an amalgam. This is then distilled as the mercury passes over and gold is left behind in the bottom. This process removes 70-80% of the gold.

• Plattner's Chlorination process

The powdered ore is roasted to remove sulfur and arsenic, it is then moistened and treated with chlorine. The gold chloride is reacted with water and treated with Ferrous sulfate to recover gold.

Refining of Gold

The above-extracted gold contains traces of impurities that can be removed by the following process.

• Fusion process 

The impure metal is fused with borax and nitre, it is oxidized and forms Scum and is removed. 

• Parting process

This is mainly to remove silver impurities. This impure metal is treated with sulphuric acid when the silver dissolves to form silver sulfate leaving the gold.

• Electrolytic refining

In this electrolytic process, the electrolyte is a 4% gold chloride solution with 10% HCl, the anode is impure gold and the cathode is a pure gold plate.

Properties

Gold is a yellow metal that melts at 1063 °C and boils at 2610 °C and the specific 

gravity is 19. 3. It is a good conductor of heat and electricity.

Gold is not affected by air (dry or moist) and water (or steam). Alkalis have no effect on gold and it is resistant to most acids but gold dissolves in aquaregia forming chloroauric acid. Gold readily forms an amalgam with mercury. It is attacked with chlorine forming auric chloride at 200 °C.

Gold Uses

• Gold is mainly used in jewelry or ornamental vessels.

• Gold plating: Gold is plated over other metals for its appearance and cost.

• Gold leaf is used in decoration and food. Some sweets and cakes are coated with gold foils.

• Medicinal: Gold has many medicinal uses one of which is the Gold complex is used to treat Rheumatoid arthritis.

• Nanoparticles: Gold nanoparticles have been widely used in many industries mainly in catalysis.

• Gold is used in electronics as it is a good conductor of electricity. It is used in electronic cables and wiring.

• Purple of Cassius: Colloidal gold is prepared by mixing a solution of gold chloride with stannous chloride. It's purple or red in color and used in making ruby-red glass and high-class pottery.