Gold Formula: Can you name the most common metal that is universally accepted in exchange for goods and services? It is the noblest of all noble metals with the highest ductility property. It’s Gold \( – {\rm{A}}\) yellow, shiny, beautiful metal and the primary component of jewellery. One gram of gold wire can be drawn into a wire of about \(2\, {\rm{ km}}\) in length. Let’s learn some more properties about gold and its chemical formula in detail.

Gold Occurrence and Extraction

Gold often occurs in nature in its elemental or native form, as nuggets or grains in the Earth’s crust. It is also found in alluvial deposits.

In the metallurgy of gold, the metal is leached with a dilute solution of \({\rm{NaCN}}\) or \({\rm{KCN}}\). The leaching process takes place in the presence of oxygen. The metal is later obtained by replacement.

\(4{\rm{Au}}({\rm{s}}) + 8{\rm{C}}{{\rm{N}}^ – }({\rm{aq}}) + 2{{\rm{H}}_2}{\rm{O}}({\rm{aq}}) + {{\rm{O}}_2}({\rm{g}}) \to 4{\left[ {{\rm{Au}}{{({\rm{CN}})}_2}} \right]^ – }({\rm{aq}}) + 4{\rm{O}}{{\rm{H}}^ – }({\rm{aq}})\)

\(2{\left[ {{\rm{Au}}{{({\rm{CN}})}_2}} \right]^ – }({\rm{aq}}) + {\rm{Zn}}({\rm{s}}) \to {\left[ {{\rm{Zn}}{{({\rm{CN}})}_4}} \right]^{2 – }}({\rm{aq}}) + 2{\rm{Au}}({\rm{s}})\)

This reaction is an oxidation reaction where zinc acts as a reducing agent.

Atomic Properties of Gold

1. Gold is a transition metal with the chemical symbol Au derived from the Latin word “aurum.”
2. Its atomic number is \(79\) and is one of the highest atomic number elements that occur naturally.
3. It belongs to the sixth period and is the third element in the copper family of the periodic table.
4. Its electronic configuration is \([{\rm{Xe}}]4{{\rm{f}}^{14}}5\;{{\rm{d}}^{10}}6\;{{\rm{s}}^1}\).
5. Its molar mass is \(196.966\, {\rm{ g}}/{\rm{mol}}\).

Physical Properties of Gold

1. Gold belongs to the transition series of metals and a group \(11\) element.
2. It is solid under standard conditions and is one of the least reactive chemical elements.
3. It is a bright, slightly reddish yellow metal in pure form.
4. It is soft, dense with the highest malleability and ductility properties.
5. One gram of gold wire can be drawn into a wire of about \(2\, {\rm{ km}}\) in length.
6. It is not just a beautiful metal but a good conductor of heat and electricity.
7. Gold has a density of \(19.3\;{\rm{g}}/{\rm{c}}{{\rm{m}}^3}\), almost identical to that of tungsten at \(19.3\;{\rm{g}}/{\rm{c}}{{\rm{m}}^3}\);
8. It has a high Melting Point around \(1064\,^\circ {\rm{C}}\) and Boiling Point around \(2970\,^\circ {\rm{C}}\).

Chemical Properties of Gold

1. Gold ranks the lowest in the activity series of metals. This accounts for its presence in the state.

\({\rm{K}}\)	Potassium		Most reactive
\({\rm{Na}}\)	Sodium
\({\rm{Ca}}\)	Calcium
\({\rm{Mg}}\)	Magnesium
\({\rm{Al}}\)	Aluminium
\({\rm{Zn}}\)	Zinc
\({\rm{Fe}}\)	Iron		Reactivity decreases
\({\rm{Pb}}\)	Lead
\({\rm{H}}\)	Hydrogen
\({\rm{Cu}}\)	Copper
\({\rm{Hg}}\)	Mercury
\({\rm{Ag}}\)	Silver
\({\rm{Au}}\)	Gold		Least Reactive

2. Gold is the most malleable metal.
3. Gold neither reacts with oxygen nor even with water.
4. It is resistant to most acids; however, it dissolves in aqua regia (a \(1:3\) ratio of nitric acid and hydrochloric acid) to form a soluble tetrachloroaurate anion.
5. Gold does not react with bases. However, it reacts with alkaline solutions sodium or potassium cyanide in the presence of oxygen to form soluble complexes.
6. Gold does not dissolve in nitric acid. However, silver and base metals dissolve in it. This property is used to refine gold and to confirm its presence in metallic substances and is known as the acid test.
7. Alkaline solutions of cyanide also dissolve gold. These are used in electroplating and mining.
8. It dissolves in mercury to form amalgam alloys.
9. Although it is the noblest of all noble metals, it still forms many diverse compounds.
10. The most common oxidation state of gold is \( + 1{\rm{Au}}({\rm{I}})\) and \( + 3{\rm{Au}}({\rm{III}})\).
11. \({\rm{Au}}({\rm{l}})\) is referred to as the aurous ion and is present in  \({\left[ {{\rm{Au}}{{({\rm{CN}})}_2}} \right]^ – }\), which is the soluble form of gold encountered in mining.
12. \({\rm{Au}}({\rm{III}})\) is referred to as the auric ion, is present in gold\(({\rm{III}})\) chloride, \({\rm{A}}{{\rm{u}}_2}{\rm{C}}{{\rm{l}}_6}\).
13. Gold is strongly attacked by fluorine to form gold(III) fluoride. Its powdered form reacts with chlorine at \(180\,^\circ {\rm{C}}\) to form \({\rm{AuC}}{{\rm{l}}_3}\) and with bromine at \({140^{\rm{o}}}{\rm{C}}\) to form gold(III) bromide. However, it reacts very slowly with iodine to form gold(III) iodide.
14. \(24\)-carat gold is the purest form of gold and is very soft. Hence, it cannot be used for making jewellery. It is alloyed with either silver or copper to make it hard. Generally, in India, \(22\)-carat gold is used for making ornaments. It means that \(22\) parts of pure gold are alloyed with two parts of either copper or silver.

Uses of Gold

1. Gold is a precious and relatively rare element.
2. It is widely used for jewellery, coinage, and other forms of art throughout history.
3. Earlier, a gold standard was often implemented as a monetary policy.
4. Gold is widely as electrical connector due to its high ductility, malleability, and resistance to corrosion and chemical reactions.
5. Due to its electricity conducting capacity, it is used in all types of computerised devices (its chief industrial use).
6. Gold is also used in gold leafing, infrared shielding, tooth restoration, and coloured-glass production.
7. Its medicinal use includes the treatment of rheumatoid arthritis under treatment called Chrysoteraphy.
8. A thin layer of gold is done on the astronaut’s helmets to protect them from UV radiation.
9. Depending on the metal with which it is alloyed, gold for jewellery can be given a range of hues (white, red, blue, green, etc.).
10. A thin film of Metallic Gold is applied on the windows of the large building to reflect Sun’s heat.
11. Copper components are often electroplated with gold to improve their solderability.

Summary

Gold, a relatively rare and precious metal that consumes around \(75\% \) of the jewellery across the world. The noblest of all noble metals is the most malleable and ductile in nature. Due to its low chemical reactivity, it occurs in the state of nature. In this article, we learned the occurrence, atomic and physical properties of gold. We also learned its chemical properties and some of its uses.

FAQs on Gold Formula

Q.1. Is gold chemically acidic or basic?
Ans: Gold is chemically inert. It ranks lowest in the activity series of metals; hence it is the least reactive.

Q.2. Does the body absorb gold chemicals?
Ans: Gold is a chemically inert noble metal. It won’t break down during digestion and will not be absorbed from the digestive system into the bloodstream. It will be eliminated from the body as waste.

Q.3. What is liquid gold?
Ans: Petroleum is known as liquid gold. It is also known as crude oil, which occurs naturally as a yellowish-black liquid. It is found in geological formations under the surface of the Earth. It is called ‘Liquid Gold’ since it is liquid, and just like gold, it has a high commercial value.

Q.4. What are the three uses of gold?
Ans: Gold is considered to be the best filling for cavities and crowns and tooth restoration.
Due to its electricity conducting capacity, it is used in all computerised devices (its chief industrial use).
Gold is widely as electrical connector due to its high ductility, malleability and resistance to corrosion and chemical reactions.

Q.5. Why aqua regia dissolves gold?
Ans: Gold is a chemically inert metal; however, it dissolves in aqua regia (\(1:3\) molar ratio of nitric acid and hydrochloric acid) mixture. This is due to the unique action of nitric and hydrochloric acid. Nitric acid is a strong oxidising agent; hence it can convert small amounts of gold to its ionic form, \({\rm{A}}{{\rm{u}}^{3 + }}\).The hydrochloric acid provides chloride anions that react with the gold cations to form tetrachloroaurate(III) anions. This equilibrium reaction favours the formation of chloroaurate anions \(\left( {{{\left[ {{\rm{AuC}}{{\rm{l}}_4}} \right]}^ – }} \right)\), the gold ions are removed from the solution. Using this method, it is possible to produce gold with a purity of \({\rm{99}}{\rm{.999\% }}\).

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