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What is Gold? – Definition, Properties, Uses and Applications

  • Last Updated : 26 Oct, 2021

Gold is frequently found in its free elemental form, as nuggets or grains, in rocks, veins, and alluvial deposits. It can be found in a solid solution series with silver, naturally alloyed with other metals like copper and palladium, and as mineral inclusions like pyrite.

Gold is a chemical element with the symbol Au and the atomic number 79, making it one of the elements with a higher atomic number that occur naturally. In its pure form, it is a bright, slightly reddish yellow, dense, soft, malleable, and ductile metal. 

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In chemistry, gold is a transition metal and a group 11 element. It is one of the least reactive chemical elements and, under normal conditions, is solid.



Occurrence of Gold

Gold is found in trace amounts in all igneous rocks. Its abundance in the Earth’s crust is estimated to be approximately 0.005 parts per million. Except for tellurium, selenium, and bismuth, it occurs mostly in its native state, remaining chemically uncombined. Gold-197 is the element’s only naturally occurring isotope.

Gold is frequently found in conjunction with copper and lead deposits, and while the amount present is often extremely small, it is easily recovered as a byproduct in the refining of those base metals. It is unusual to find large masses of gold-bearing rock rich enough to be called ores. There are two types of gold deposits known: hydrothermal veins, where it is associated with quartz and pyrite, and placer deposits, both consolidated and unconsolidated, which are formed by the weathering of gold-bearing rocks.

Properties of Gold

  • It is extremely rare, will not rust, and is non-toxic.
  • The element is corrosion resistant and can be found in alluvium and vein deposits.
  • Although copper and silver are the best conductors of heat and electricity, gold connections outlast both because they do not tarnish. It is not so much that gold lasts longer as it is that it remains conducive for a longer period of time.
  • Gold is ductile: It has the ability to be drawn out into the thinnest wire. One ounce of gold can be drawn into 80 kilometres of five microns, or five millionths of a metre, thick gold wire. This sample has a diameter of 0.20 millimetres.
  • As gold is highly reflective of heat and light, the visors of astronauts’ space helmets are coated with a thin, partially transparent layer of gold. Even though the astronauts can see through it, the gold film reduces glare and heat from the sun.
  • Gold is prized for its beauty: Gold is typically alloyed in jewellery to increase its strength, and the term carat refers to the amount of gold present (24 carats is pure gold). Jewellers and metalsmiths prize it as a versatile metal that may be embossed, hammered, cast, stretched, or twisted.
  • As gold is malleable, it can be flattened into extremely thin sheets. The Gold Room’s walls are coated in about 28 square metres of 23-karat gold leaf, which is the equivalent of 3 ounces of gold metal. One ounce of gold can be hammered thin enough to cover a surface larger than 9 square metres.

Uses and Applications of Gold

  1. Gold is used as a bouillon, as well as in jewellery, glass, and electronics. Jewellery consumes approximately 75% of all gold produced. Gold for jewellery can be coloured in a variety of ways depending on the metal with which it is alloyed. Colloidal gold is used to colour glass red or purple, and metallic gold is used as a thin film on large building windows to reflect the heat of the Sun’s rays. In the electronic industry, gold electroplating is used to protect copper components and improve solderability.
  2. Gold is the only material that is universally accepted in exchange for goods and services due to its unique properties. Although silver was generally the standard medium of payment in the world’s trading systems, gold has played an important role as a high-denomination currency in the form of coins or bullion on occasion.
  3. Metal is primarily used in the production of jewellery, glass, and various components in electronic devices.
  4. Gold thread can be made and used in embroidery.
  5. A thin layer of this metal is used to reflect the heat of the sun’s rays on the windows of a large building.
  6. In addition, gold is used in medicine. Its radioactive isotope Au-198 is used in tumour treatment.

Synthesis of Gold

The prospect of generating gold from a more common element, such as lead, has long piqued people’s interest, and alchemy, an ancient and mediaeval science, regularly concentrated on it. However, the transmutation of chemical elements did not become possible until the twentieth century, with the understanding of nuclear physics.

Hamtaro Nagaoka, a Japanese physicist, was the first to use neutron bombardment to synthesize gold from mercury in 1924. An American team, unaware of Nagaoka’s previous research, carried out the same experiment in 1941, achieving the same result and demonstrating that the gold isotopes produced by it were all radioactive. Gold can now be made in a nuclear reactor by irradiating platinum or mercury with neutrons.

Sample Questions

Question 1: Explain why pure gold is not suitable for making ornaments.

Answer:

As pure gold is very soft and prone to wear and tear when used, ornaments made of 24-carat gold, which is pure gold, are extremely rare. As a result, 22-carat gold is commonly used, which contains a trace of copper, silver, and other metals to improve wear resistance while also retaining its elegance.

Question 2: How does gold occur with other elements in nature?



Answer:

Gold is frequently found in conjunction with copper and lead deposits, and while the amount present is often extremely small, it is easily recovered as a byproduct in the refining of those base metals. It is unusual to find large masses of gold-bearing rock rich enough to be called ores. There are two types of gold deposits known: hydrothermal veins, where it is associated with quartz and pyrite, and placer deposits, both consolidated and unconsolidated, which are formed by the weathering of gold-bearing rocks.

Question 3: Arrange the metals gold, copper, iron and magnesium in order of their increase in reactivity.

Answer:

Au < Cu < Fe < Mg is increasing order of reactivity.

Question 4: Explain why platinum, gold, and silver are used in the manufacture of jewellery.

Answer:

Platinum, gold, and silver are used to make jewellery because they are low reactive metals with little corrosion (in silver) and thus retain their shine and lustre.

Question 5: How is gold used as a commodity?

Answer:

As gold has distinct properties, it is the only material that is universally accepted in exchange for goods and services. Although silver was generally the standard medium of payment in the world’s trading systems, gold has played an important role as a high-denomination currency in the form of coins or bullion on occasion.

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