The Element Gold
Introduction to Gold
The element gold is a well-known transition metal with atomic number 79. It has malleable, conductive, and ductile metal properties, and its bright, attractive color makes it a very valuable metal.
10 Fun Facts About Gold
- Gold is the most malleable and ductile element on the periodic table.
- When flattened, 1 ounce of gold can produced 187 square feet of gold sheets.
- Gold does not corrode or tarnish, making it a very durable and thus attractive metal.
- Gold served as a backing for paper currency in the US from the 19th century all the way up to the 1933. All nations still accept it as a medium of exchange today.
- International reserves hold 45% of all gold in the world.
- Because it is so soft, gold usually forms alloys with other metals such as silver for use in jewelry.
- Gold is one of the least reactive transition metals—it does not react with oxygen or sulfur.
- One of the most famous applications of gold is in Egyptian pharaoh King Tut’s burial mask.
- Gold is edible in small amounts. Some luxurious restaurants like to add gold leaf, or small pieces of gold sheet, onto their dishes for decoration.
- In the 1848 Gold Rush, settlers discovered gold in California, causing an influx of new migrants.
Gold in the Periodic Table
Gold, symbol Au, has an atomic number of 79. It is located in the d-block on the periodic table, with platinum to its left and mercury on its right. It is a very nonreactive transition metal in group 11, period 6, with 1 valence electron. Silver and copper are also in group 11, although gold is not that similar to them chemically.
Gold’s electronegativity is 2.54. It is one of the six precious metals. The gold atom has an electron configuration of [Xe] 4f14 5d10 6s1
The Gold Standard
Until 1933, the United States used the gold standard, in which gold backed the paper currency. In other words, the value of a dollar was based on an amount of gold, and gold could be exchanged for an amount of paper currency.
Because of its malleability, relative ease of melting, and attractiveness, gold was extremely valuable and was a form of currency in ancient civilizations. Compared to other elements, gold was relatively rare in nature, but there was still a substantial amount of it for it to back currencies. It is also non-toxic and fairly nonreactive, and thus would not tarnish or rust and would still be feasible to store. For these reasons, gold was a form of currency and backed paper currencies internationally.
Gold in the Environment
As a relatively rare element, gold’s abundance in Earth’s crust is estimated to be around 0.005 parts per million. In nature, it is usually chemically pure or in combination with tellurium, selenium, or bismuth. Gold only exists in the world in its gold-197 isotope form. It is usually found in and mined from quartz veins or placer deposits.
Gold mining is extremely destructive to the environment. Processes such as open-pit mining strip away at the land, leaving toxic wastes that are harmful to humans, plants, and animals. Toxic elements such as mercury and cyanide are byproducts of gold mining. Mining companies dump the toxic wastes into natural water bodies, where they contaminate the water and have even more adverse effects on the environment.
Gold’s Applications in Today’s World
What is gold used for?
The element gold is a very dense, malleable, conductive, ductile, and attractive metal. Because of these properties, many ancient decorations, art pieces, and currencies contained gold. In jewelry, it forms alloys with other metals to make the jewelry harder and thus more durable. Plating contacts and gold bonding wire in electronics contain gold because of the element’s high electrical conductivity. In dentistry, gold combines alloys to create gold crowns.
Gold is also used as a nanoparticle in immunolabeling experiments in biological transmission electron microscopy to localize proteins in cells and tissues
Gold in Olympic Medals
Olympic gold medals are not pure gold, with silver making up at least 92.5% of the gold medals. The element gold is mainly used to coat and plate the exterior of the medal. In the 2020 Tokyo Olympics, the host country recycled small electronics devices and parts into the gold medals, being the first country to do so. These medals have a mass of 556 grams in total.
Where is gold found?
Gold exists naturally in quartz veins or placer deposits. The element is mined in the United States, Canada, South Africa, Russia, China, and Australia. China is currently the world’s largest producer of gold, followed by Russia. The world mines around 2500-3000 tons of gold each year.
When and How was the Element Gold Discovered?
Who discovered gold? Gold was first mined by the ancient Egyptians back in 3000 BCE. Decorations and art pieces featured gold because of its attractiveness and metal properties. Egyptian pharaoh King Tut’s tomb was made of gold and also contained large amounts of gold inside.
The word “gold” originated from the Latin word aurum, “meaning glowing dawn”.
Gold Chemistry – compounds, reactions, oxidation states
Chemical Properties of Gold
Gold is one of the least reactive transition metals. Oxygen and most strong acids do not attack it.
Gold Compounds & Reactions
While gold does not react with oxygen or sulfur, the element will react with halogens. Aqua regia, a mixture of 1 part nitric and 3 parts hydrochloric acids, will dissolve gold. Aqua regia works because the nitric acid oxidizes the gold, and the hydrochloric acid forms a soluble gold complex, the tetrachloroaurate ion, AuCl4–, in the form of chloroauric acid. The reaction is Au + HNO3 + 4 HCl → HAuCl4 +NO + 2 H2O
In addition, gold will dissolve in cyanide solutions in the presence of air or hydrogen peroxide to form the stable dicyanoaurate ion, [Au(CN)2]– .
Some famous compounds of gold include gold (I) chloride (AuCl), gold (III) chloride (AuCl3), and chlorauric acid HAuCl4. Gold-plating baths also contain potassium cyanoaurate, K[Au(CN)2].
Gold compounds, as opposed to elemental gold, are actually fairly toxic and should be handled with care.
Isolation of Gold
In industrial gold mining, a process called leaching separates gold from impurities. Cyanide and oxygen react and dissolve gold, which combines with carbon in a process called carbon-in-pulp. Then, the gold and carbon undergo a process called electrowinning, where an electric current passes through the mixture to separate the two elements. This process causes the gold to collect on the negative terminal. After smelting and more refining, industrial gold is produced!
In the chemistry lab, almost any metal or reducing agent, such as sodium metabisulfite, can be sure to precipitate elemental gold from a solution of a gold compound.
Gold Oxidation States
Gold exists mainly in the +1 and +3 oxidation states, though the +1 state is generally unstable.
Physical Properties of Gold
Gold is the most malleable of all metals. In fact, just one gram can be hammered down into a sheet that is 1 square meter. It is bright yellow, extremely dense, soft and ductile. It also has high thermal conductivity.
- Symbol: Au
- Melting point: 1064℃
- Boiling point: 2966℃
- Density: 19.3 g/cm3
- Atomic weight: 196.97 u
- Atomic number: 79
- Electronegativity: 2.54
- Classification: group 11 transition metal
- Natural abundance of gold in the Earth’s crust: 0.005 ppm
- Electron shell configuration: [Xe] 4f145d106s1
- Isotopes – gold-197
- Found naturally in the minerals: sylvanite, calaverite
- Toxicity: gold is nontoxic
Where can I Buy Gold?
Gold can be bought almost anywhere if you have enough money. Gold foil is a less expensive source of gold, because of how lightweight it is.