| Discovery date | approx 3000BC |
| Discovered by | - |
| Origin of the name | The name is the Anglo-Saxon word for the metal and the symbol comes from the Latin ‘aurum’, gold. |
| Allotropes |
|
Au
Gold
79
196.967
| Group | 11 | Melting point | 1064.18°C, 1947.52°F, 1337.33 K |
| Period | 6 | Boiling point | 2836°C, 5137°F, 3109 K |
| Block | d | Density (g cm−3) | 19.3 |
| Atomic number | 79 | Relative atomic mass | 196.967 |
| State at 20°C | Solid | Key isotopes | 197Au |
| Electron configuration | [Xe] 4f145d106s1 | CAS number | 7440-57-5 |
| ChemSpider ID | 22421 | ChemSpider is a free chemical structure database | |
Image explanation
In this image a traditional alchemical symbol for the element is used. It is also used as a sun symbol, and much of the mythology around gold relates to the sun. Early alchemists were obsessed by gold and pursued their desire to transmute base metals (usually lead) into gold. The image in the background is based on a symbolic representation of an alchemist’s ‘laboratory’.
Appearance
A soft metal with a characteristic yellow colour. It is chemically unreactive, although it will dissolve in aqua regia (a mixture of nitric and hydrochloric acids).
Uses
Most mined gold is stored as bullion. It is also, however, used extensively in jewellery, either in its pure form or as an alloy. The term ‘carat’ indicates the amount of gold present in an alloy. 24-carat is pure gold, but it is very soft. 18- and 9-carat gold alloys are commonly used because they are more durable.
The metal is also used for coinage, and has been used as standard for monetary systems in some countries.
Gold can be beaten into very thin sheets (gold leaf) to be used in art, for decoration and as architectural ornament. Electroplating can be used to cover another metal with a very thin layer of gold. This is used in gears for watches, artificial limb joints, cheap jewellery and electrical connectors. It is ideal for protecting electrical copper components because it conducts electricity well and does not corrode (which would break the contact). Thin gold wires are used inside computer chips to produce circuits.
Dentists sometimes use gold alloys in fillings, and a gold compound is used to treat some cases of arthritis.
Gold nanoparticles are increasingly being used as industrial catalysts. Vinyl acetate, which is used to make PVA (for glue, paint and resin), is made using a gold catalyst.
Biological role
Gold has no known biological role, and is non-toxic.
Natural abundance
Gold is one of the few elements to occur in a natural state. It is found in veins and alluvial deposits. About 1500 tonnes of gold are mined each year. About two-thirds of this comes from South Africa and most of the rest from Russia.
Seawater contains about 4 grams of gold in 1,000,000 tonnes of water. Overall this is a huge amount of gold stored in the oceans but, because the concentration is so low, attempts to reclaim this gold have always failed.
Gold has been known since prehistoric times and was one of the first metals to be worked, mainly because it was to be found as nuggets or as particles in the beds of streams. Such was the demand that by 2000 BC the Egyptians began mining gold. The death mask of Tutankhamen, who died in 1323 BC, contained 100 kg of the metal. The royal graves of ancient Ur (modern Iraq), which flourished from 3800 to 2000 BC, also contained gold objects.
The minting of gold coins began around 640 BC in the Kingdom of Lydia (situated in what is now modern Turkey) using electrum, a native alloy of gold and silver. The first pure gold coins were minted in the reign of King Croesus, who ruled from 561–547 BC.
| Atomic radius, non-bonded (Å) | 2.14 | Covalent radius (Å) | 1.30 |
| Electron affinity (kJ mol−1) | 222.749 |
Electronegativity (Pauling scale) |
2.4 |
|
Ionisation energies (kJ mol−1) |
1st
890.128
2nd
1949
3rd
-
4th
-
5th
-
6th
-
7th
-
8th
-
|
||
| Common oxidation states | 5,4,3,2, 1,-1 | ||||
| Isotopes | Isotope | Atomic mass | Natural abundance (%) | Half life | Mode of decay |
| 197Au | 196.967 | 100 | - | - | |
| 198Au | 197.968 | - | 2.695 d | β- | |
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|
Specific heat capacity (J kg−1 K−1) |
129 | Young's modulus (GPa) | 78.0 | |||||||||||
| Shear modulus (GPa) | 27.0 | Bulk modulus (GPa) | 217.0 | |||||||||||
| Vapour pressure | ||||||||||||||
| Temperature (K) |
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| Pressure (Pa) |
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| Listen to Gold Podcast |
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Transcript :
Chemistry in its element: gold (Promo) You're listening to Chemistry in its element brought to you by Chemistry World, the magazine of the Royal Society of Chemistry. (End promo) Chris Smith Hello, in this week's episode of Chemistry in its element, we're taking a flight on Concorde, dropping by Buckingham Palace and finding out what could form a film just 230 atoms thick. Going for gold for us this week, here's the legendary science broadcaster and populariser Johnny Ball. Johnny Ball The element gold. Gold is element 79 and its symbol is Au. Though the name is Anglo Saxon, gold originated from the Latin Aurum, or shining dawn, and previously from the Greek. It's abundance in the earth's crust is 0.004 ppm. 100% of gold found naturally is isotope Au-197. 28 other isotopes can be produced artificially and are all radioactive. Gold along with silver and copper, form a column in the periodic table. They are found naturally and were the first three elements known to man. They were all used as primitive money well before the first gold coins which appeared in Egypt around 3400 BC. Most gold is ancient or comes from Central American Aztecs and South American Incas brought to Europe by the Spanish and Portuguese in the 16th century, and which has since been recycled over and over again. In 1830 world output was no more than 12 tonnes per annum. But around that time, new gold discoveries were being made. Finds were discovered in Siberia, California, New South Wales and Victoria, Australia, Transvaal, South Africa, the Klondike and Alaska, and they all produced gold rushes. World production was then around 150 tonnes per year. It is now around 2300 tones per annum. Because it is found in it's natural state and does not naturally alloy with anything else and because it is the heaviest metal, by sifting rock in water, the gold always falls to the bottom and all less dense impurities are washed away. The largest nugget was the Welcome Stranger nugget found in Victoria, Australia in 1869. It weighed over 71 kg. This type of nugget occurs naturally, but is very, very rare. Pure gold is 24 karat. 18 karat is 75% and 12 karat is 50% pure gold. Gold is the most malleable of all metals and soft enough to be cut with a knife. Stone age peoples hammered gold into plates for ornamental purposes. Really quite large amounts were gathered together. Though King Tutankhamun was a minor Pharaoh and died aged 18, his coffin alone contained 112 kg of gold. Egyptians also made thin gold sheets, utensils, vast varieties of jewellery and even gold thread. King Tut when he was buried had over 150 gold ornaments on his body. Today 1 gram can be beaten into a square metre sheet just 230 atoms thick. 1 cubic centimetre would make a sheet of 18 square metres. Concord's windscreen had a layer of gold to screen pilots from UV light and today it is often used in sky scraper windows to cut down both heat and UV from sunlight. 1 gram can be drawn to make 165 metres of wire 20 um (microns) thick (1/200th of a millimeter) The gold colour in the Buckingham Palace fence is actually gold covered, as it lasts 30 years, whereas gold paint (which contains no gold at all) lasts in tip top condition, only about a year. Sea water contains around 3 parts in a billion of gold, but there's never been found an economic means of recovering it. The Germans tried very hard during the second World War but failed miserably. The largest modern hoard is the 30,000 tons in the US Federal Reserve Bank in New York, which belongs to 18 different nations. It is estimated that all the world's gold gathered together would only make a cube around 18 metres per side - about 6000 cubic metres. And that's gold. Chris Smith So now you know why pirates used to bite gold coins to see if they were real. It wasn't just for the camera because it looked good, it was because the metal was soft enough to be marked by teeth. That was Johnny Ball telling the story of gold. Next time on Chemistry in its element Victoria Gill introduces the chemical that founded the science of photography and also helped to launch the careers of successions of Oscar winners. Victoria Gill in 1840, Henry Talbot discovered an additional chemical twist, that a so called latent silver image, that had been briefly exposed onto a layer of silver iodide could be revealed using gallic acid. The effect was seen as magical, a devilish art. Hollywood could never have existed without the chemical reaction that gave celluloid film its ability to capture the stars and bring them to the aptly dubbed silver screen. Chris Smith And you can hear Victoria Gill crossing your cognitive palm and lining your intellectual pocket with silver on next week's Chemistry in its element. I'm Chris Smith, thank you for listening, see you next time. (Promo) Chemistry in its element is brought to you by the Royal Society of Chemistry and produced by thenakedscientists.com. There's more information and other episodes of Chemistry in its element on our website at chemistryworld.org/elements. (End promo)
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Visual Elements images and videos
© Murray Robertson 1998-2017.
W. M. Haynes, ed., CRC Handbook of Chemistry and Physics, CRC Press/Taylor and Francis, Boca Raton, FL, 95th Edition, Internet Version 2015, accessed December 2014.
Tables of Physical & Chemical Constants, Kaye & Laby Online, 16th edition, 1995. Version 1.0 (2005), accessed December 2014.
J. S. Coursey, D. J. Schwab, J. J. Tsai, and R. A. Dragoset, Atomic Weights and Isotopic Compositions (version 4.1), 2015, National Institute of Standards and Technology, Gaithersburg, MD, accessed November 2016.
T. L. Cottrell, The Strengths of Chemical Bonds, Butterworth, London, 1954.
John Emsley, Nature’s Building Blocks: An A-Z Guide to the Elements, Oxford University Press, New York, 2nd Edition, 2011.
Thomas Jefferson National Accelerator Facility - Office of Science Education, It’s Elemental - The Periodic Table of Elements, accessed December 2014.
Periodic Table of Videos, accessed December 2014.
Derived in part from material provided by the British Geological Survey © NERC.
Elements 1-112, 114, 116 and 117 © John Emsley 2012. Elements 113, 115, 117 and 118 © Royal Society of Chemistry 2017.
Produced by The Naked Scientists.
Created by video journalist Brady Haran working with chemists at The University of Nottingham.
© Murray Robertson 1998-2017.
Data
W. M. Haynes, ed., CRC Handbook of Chemistry and Physics, CRC Press/Taylor and Francis, Boca Raton, FL, 95th Edition, Internet Version 2015, accessed December 2014.
Tables of Physical & Chemical Constants, Kaye & Laby Online, 16th edition, 1995. Version 1.0 (2005), accessed December 2014.
J. S. Coursey, D. J. Schwab, J. J. Tsai, and R. A. Dragoset, Atomic Weights and Isotopic Compositions (version 4.1), 2015, National Institute of Standards and Technology, Gaithersburg, MD, accessed November 2016.
T. L. Cottrell, The Strengths of Chemical Bonds, Butterworth, London, 1954.
Uses and properties
John Emsley, Nature’s Building Blocks: An A-Z Guide to the Elements, Oxford University Press, New York, 2nd Edition, 2011.
Thomas Jefferson National Accelerator Facility - Office of Science Education, It’s Elemental - The Periodic Table of Elements, accessed December 2014.
Periodic Table of Videos, accessed December 2014.
Supply risk data
Derived in part from material provided by the British Geological Survey © NERC.
History text
Elements 1-112, 114, 116 and 117 © John Emsley 2012. Elements 113, 115, 117 and 118 © Royal Society of Chemistry 2017.
Podcasts
Produced by The Naked Scientists.
Periodic Table of Videos
Created by video journalist Brady Haran working with chemists at The University of Nottingham.
