Characteristics and Properties of Gold
– Gold is the most malleable of all metals.
– It can be drawn into a wire of single-atom width.
– Gold can be beaten into a sheet of 1 square meter.
– Gold leaf can be beaten thin enough to become semi-transparent.
Gold is a good conductor of heat and electricity.
– Gold is slightly reddish-yellow in color.
– The color is determined by plasma oscillations among the metals valence electrons.
– Relativistic effects affect the orbitals around gold atoms, giving it a golden hue.
– Different alloys can produce colored gold, such as rose gold, white gold, green gold, blue gold, and purple gold.
– Colloidal gold appears red when particles are small and blue when particles are larger.
– Gold has only one stable isotope, 197Au.
– Thirty-six radioisotopes of gold have been synthesized.
– The most stable radioisotope is 195Au with a half-life of 186.1 days.
Gold’s radioisotopes decay through various processes such as proton emission, alpha decay, beta decay, and electron capture.
– Gold also has nuclear isomers, with 198m2Au being the most stable.
– Gold often occurs in free elemental form as nuggets or grains.
– It is found in rocks, veins, and alluvial deposits.
– Gold can form solid solutions with silver and be naturally alloyed with other metals like copper and palladium.
Gold compounds can occur in minerals, often with tellurium.
– Gold is a relatively rare element.
– Gold has been used for coinage, jewelry, and art throughout history.
– It was once used as a monetary standard.
– Gold is used in electrical connectors, infrared shielding, colored glass production, gold leafing, and tooth restoration.
– Certain gold salts have medical applications as anti-inflammatories.
– China is the world’s largest gold producer, followed by Russia and Australia.

Synthesis and Chemistry of Gold
Gold has three decay paths: β decay, isomeric transition, and alpha decay.
– No other isomer or isotope of gold has three decay paths.
– The first synthesis of gold was conducted by Japanese physicist Hantaro Nagaoka in 1924 by neutron bombardment of mercury.
– An American team conducted the same experiment in 1941, achieving the same result and showing that the isotopes of gold produced were all radioactive.
– In 1980, Glenn Seaborg transmuted several thousand atoms of bismuth into gold.
– Gold can be manufactured in a nuclear reactor, but it is highly impractical and costly.
– Gold forms diverse compounds with oxidation states ranging from -1 to +5.
– Au(I) compounds are typically linear and commonly encountered in mining.
– Au(III) compounds have square planar structures and can form mixed-valence complexes.
– Gold does not react with oxygen or most acids, but can react with halogens and form gold sulfide.
– Gold readily dissolves in mercury at room temperature and forms alloys with other metals.
– Gold can exhibit oxidation states of -1, +2, and +5.
– Aurides, compounds containing the auride anion, can have gold in the -1 oxidation state.
Gold(II) compounds are usually diamagnetic and form Au-Au bonds.
– Gold(II) sulfate contains Au4+2 cations, similar to the mercury(I) ion.
– Gold(V) is represented by gold pentafluoride, its derivative anion, and gold heptafluoride.

Occurrence of Gold
– Gold is thought to have been produced in supernova nucleosynthesis and from the collision of neutron stars.
– It is also believed to have been present in the dust from which the Solar System formed.
– Traditionally, gold in the universe is thought to have formed by the r-process in supernova nucleosynthesis.
– Recent studies suggest that gold and other heavy elements may also be produced in neutron star mergers.
– Spectroscopic signatures of gold and other heavy elements were observed in the GW170817 neutron star merger event.
– Gold in Earth’s crust and mantle may have been delivered by asteroid impacts during the Late Heavy Bombardment.
– The asteroid that formed the Vredefort impact structure is associated with the richest gold deposits in the Witwatersrand basin.
– The gold-bearing Witwatersrand rocks were laid down before the Vredefort impact.
– The impact distorted the Witwatersrand basin, bringing the gold-bearing rocks to the surface.
– The discovery of the deposit in 1886 led to the Witwatersrand Gold Rush.
– Gold on Earth is thought to have been incorporated into the planet since its formation.
– Scientists found evidence of gold coming from the mantle at Deseado Massif in Argentina.
– Further research is needed for clarification.
– Gold is found in ores in rock formed from the Precambrian time onward.
– It often occurs as a native metal or in gold/silver alloys.
– Native gold is found in lode deposits or as free flakes, grains, or nuggets in alluvial deposits.
– Gold can occur with tellurium minerals and in rare alloys with copper, lead, and mercury.
– Microbes and earthquakes can also play a role in forming gold deposits.
Gold is present in the world’s oceans, but at very low concentrations.
– Gold concentrations in the Atlantic and Northeast Pacific are 50-150 femtomol/L.
– Mediterranean deep waters have slightly higher concentrations.
– Claims of economically recovering gold from seawater have been proven to be false.
– Previous data on gold concentrations in seawater were contaminated.

Historical Significance of Gold
– The oldest recorded gold artifacts date back to the late Paleolithic period, around 40,000 BC.
– The Varna Necropolis in Bulgaria contains the oldest well-dated gold artifacts, dating back to the 5th millennium BC.
– Gold artifacts also appeared in Ancient Egypt and Lower Mesopotam

Merriam-Webster Online Dictionary
gold (noun)
1.
a yellow malleable ductile metallic element that occurs chiefly free or in a few minerals and is used especially in coins, jewelry, and dentures - see element table
2.
a) (1) gold coins
(2) a gold piece
b) - money
c) - gold standard
3.
a variable color averaging deep yellow
4.
something resembling gold , especially something valued as the finest of its kind - a heart of gold
5.
a medal awarded as the first prize in a competition a gold medal
gold (adjective)
qualifying for a gold record
Merriam-Webster Online Thesaurus
gold (noun)
something (as pieces of stamped metal or printed paper) customarily and legally used as a medium of exchange, a measure of value, or a means of payment
SYNONYMS:
bread, bucks, cabbage, cash, change, chips, coin, currency, dough, gold, green, jack, kale, legal tender, lolly, long green, loot, lucre, moola ( moolah), needful, pelf, scratch, shekels ( sheqels shekelim shekalim sheqalim), tender, wampum
RELATED WORDS:
coinage, specie; dead presidents [], folding money, paper money, scrip; banknote, cashier's check, check, draft, money order, note, promissory note; bill, dollar, greenback; bankroll, capital, finances, funds, roll [], wad, wallet; chump change, dibs [], dime, mite, peanuts, pittance, shoestring; big bucks, bomb [], boodle, bundle, earth, fortune, king's ransom, megabucks, mint, packet [], pile, pot; abundance, means, opulence, riches, treasure, wealth; resources, wherewithal; mad money, petty cash, pin money, pocket money, spending money
Gold (Wikipedia)

Gold is a chemical element; it has the symbol Au (from the Latin word "aurum") and the atomic number 79. In its pure form, it is a bright, slightly orange-yellow, dense, soft, malleable, and ductile metal. Chemically, gold is a transition metal, a group 11 element, and one of the noble metals. It is one of the least reactive chemical elements, being the second-lowest in the reactivity series. It is solid under standard conditions.

Gold, 79Au
Gold
AppearanceMetallic yellow
Standard atomic weight Ar°(Au)
  • 196.966570±0.000004
  • 196.97±0.01 (abridged)
Gold in the periodic table
Hydrogen Helium
Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon
Sodium Magnesium Aluminium Silicon Phosphorus Sulfur Chlorine Argon
Potassium Calcium Scandium Titanium Vanadium Chromium Manganese Iron Cobalt Nickel Copper Zinc Gallium Germanium Arsenic Selenium Bromine Krypton
Rubidium Strontium Yttrium Zirconium Niobium Molybdenum Technetium Ruthenium Rhodium Palladium Silver Cadmium Indium Tin Antimony Tellurium Iodine Xenon
Caesium Barium Lanthanum Cerium Praseodymium Neodymium Promethium Samarium Europium Gadolinium Terbium Dysprosium Holmium Erbium Thulium Ytterbium Lutetium Hafnium Tantalum Tungsten Rhenium Osmium Iridium Platinum Gold Mercury (element) Thallium Lead Bismuth Polonium Astatine Radon
Francium Radium Actinium Thorium Protactinium Uranium Neptunium Plutonium Americium Curium Berkelium Californium Einsteinium Fermium Mendelevium Nobelium Lawrencium Rutherfordium Dubnium Seaborgium Bohrium Hassium Meitnerium Darmstadtium Roentgenium Copernicium Nihonium Flerovium Moscovium Livermorium Tennessine Oganesson
Ag

Au

Rg
platinumgoldmercury
Atomic number (Z)79
Groupgroup 11
Periodperiod 6
Block  d-block
Electron configuration[Xe] 4f14 5d10 6s1
Electrons per shell2, 8, 18, 32, 18, 1
Physical properties
Phase at STPsolid
Melting point1337.33 K ​(1064.18 °C, ​1947.52 °F)
Boiling point3243 K ​(2970 °C, ​5378 °F)
Density (at 20° C)19.283 g/cm3
when liquid (at m.p.)17.31 g/cm3
Heat of fusion12.55 kJ/mol
Heat of vaporization342 kJ/mol
Molar heat capacity25.418 J/(mol·K)
Vapor pressure
P (Pa) 1 10 100 1 k 10 k 100 k
at T (K) 1646 1814 2021 2281 2620 3078
Atomic properties
Oxidation states−3, −2, −1, 0, +1, +2, +3, +5 (an amphoteric oxide)
ElectronegativityPauling scale: 2.54
Ionization energies
  • 1st: 890.1 kJ/mol
  • 2nd: 1980 kJ/mol
Atomic radiusempirical: 144 pm
Covalent radius136±6 pm
Van der Waals radius166 pm
Color lines in a spectral range
Spectral lines of gold
Other properties
Natural occurrenceprimordial
Crystal structureface-centered cubic (fcc) (cF4)
Lattice constant
Face centered cubic crystal structure for gold
a = 407.86 pm (at 20 °C)
Thermal expansion14.13×10−6/K (at 20 °C)
Thermal conductivity318 W/(m⋅K)
Electrical resistivity22.14 nΩ⋅m (at 20 °C)
Magnetic orderingdiamagnetic
Molar magnetic susceptibility−28.0×10−6 cm3/mol (at 296 K)
Tensile strength120 MPa
Young's modulus79 GPa
Shear modulus27 GPa
Bulk modulus180 GPa
Speed of sound thin rod2030 m/s (at r.t.)
Poisson ratio0.4
Mohs hardness2.5
Vickers hardness188–216 MPa
Brinell hardness188–245 MPa
CAS Number7440-57-5
History
Namingfrom Latin aurum 'gold'
DiscoveryIn the Middle East (before 6000 BCE)
Symbol"Au": from Latin aurum
Isotopes of gold
Main isotopes Decay
abun­dance half-life (t1/2) mode pro­duct
195Au synth 186.01 d ε 195Pt
196Au synth 6.165 d β+ 196Pt
β 196Hg
197Au 100% stable
198Au synth 2.69464 d β 198Hg
199Au synth 3.139 d β 199Hg
 Category: Gold
| references

Gold often occurs in free elemental (native state), as nuggets or grains, in rocks, veins, and alluvial deposits. It occurs in a solid solution series with the native element silver (as in electrum), naturally alloyed with other metals like copper and palladium, and mineral inclusions such as within pyrite. Less commonly, it occurs in minerals as gold compounds, often with tellurium (gold tellurides).

Gold is resistant to most acids, though it does dissolve in aqua regia (a mixture of nitric acid and hydrochloric acid), forming a soluble tetrachloroaurate anion. Gold is insoluble in nitric acid alone, which dissolves silver and base metals, a property long used to refine gold and confirm the presence of gold in metallic substances, giving rise to the term 'acid test'. Gold dissolves in alkaline solutions of cyanide, which are used in mining and electroplating. Gold also dissolves in mercury, forming amalgam alloys, and as the gold acts simply as a solute, this is not a chemical reaction.

A relatively rare element, gold is a precious metal that has been used for coinage, jewelry, and other works of art throughout recorded history. In the past, a gold standard was often implemented as a monetary policy. Gold coins ceased to be minted as a circulating currency in the 1930s, and the world gold standard was abandoned for a fiat currency system after the Nixon shock measures of 1971.

In 2020, the world's largest gold producer was China, followed by Russia and Australia. As of 2020, a total of around 201,296 tonnes of gold exist above ground. This is equal to a cube, with each side measuring roughly 21.7 meters (71 ft). The world's consumption of new gold produced is about 50% in jewelry, 40% in investments, and 10% in industry. Gold's high malleability, ductility, resistance to corrosion and most other chemical reactions, and conductivity of electricity have led to its continued use in corrosion-resistant electrical connectors in all types of computerized devices (its chief industrial use). Gold is also used in infrared shielding, the production of colored glass, gold leafing, and tooth restoration. Certain gold salts are still used as anti-inflammatory agents in medicine.

Gold (Wiktionary)

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