Gold

This article is about the metal. For the color, see Gold (color). For other uses, see Gold (disambiguation).

79 platinum ← gold → mercury Ag ↑ Au ↓ Rg Periodic Table - Extended Periodic Table
General
Name, Symbol, Number	gold, Au, 79
Element category	transition metals
Group, Period, Block	11, 6, d
Appearance	metallic yellow
Standard atomic weight	196.966569(4)  g·mol−1
Electron configuration	[Xe] 4f14 5d10 6s1
Electrons per shell	2, 8, 18, 32, 18, 1
Physical properties
Phase	solid
Density (near r.t.)	19.3  g·cm−3
Liquid density at m.p.	17.31  g·cm−3
Melting point	1337.33 K (1064.18 °C, 1947.52 °F)
Boiling point	3129 K (2856 °C, 5173 °F)
Heat of fusion	12.55  kJ·mol−1
Heat of vaporization	324  kJ·mol−1
Specific heat capacity	(25 °C) 25.418  J·mol−1·K−1
Vapor pressure P(Pa) 1 10 100 1 k 10 k 100 k at T(K) 1646 1814 2021 2281 2620 3078
Atomic properties
Crystal structure	cubic face centered
Oxidation states	−1, 1, 2, 3, 4, 5 (amphoteric oxide)
Electronegativity	2.54 (Pauling scale)
Ionization energies	1st: 890.1 kJ/mol
	2nd: 1980 kJ/mol
Atomic radius	135  pm
Atomic radius (calc.)	174  pm
Covalent radius	144  pm
Van der Waals radius	166 pm
Miscellaneous
Magnetic ordering	diamagnetic
Electrical resistivity	(20 °C) 22.14 n Ω·m
Thermal conductivity	(300 K) 318  W·m−1·K−1
Thermal expansion	(25 °C) 14.2  µm·m−1·K−1
Speed of sound (thin rod)	(r.t.) (hard-drawn) 2030  m·s−1
Young's modulus	78  GPa
Tensile strain	0.00157
Shear modulus	27  GPa
Bulk modulus	180  GPa
Poisson ratio	0.44
Mohs hardness	2.5
Vickers hardness	216  MPa
Brinell hardness	? 2450  MPa
CAS registry number	7440-57-5
Most-stable isotopes
Main article: Isotopes of gold iso NA half-life DM DE (MeV) DP 195Au syn 186.10 d ε 0.227 195Pt 196Au syn 6.183 d ε 1.506 196Pt β- 0.686 196Hg 197Au 100% 197Au is stable with 118 neutrons 198Au syn 2.69517 d β- 1.372 198Hg 199Au syn 3.169 d β- 0.453 199Hg
References

Gold (pronounced /ˈɡoʊld/) is a chemical element with the symbol Au (Latin: aurum) and atomic number 79. It is a highly sought-after precious metal in jewelry, in sculpture, and for ornamentation since the beginning of recorded history. The metal occurs as nuggets or grains in rocks, in veins and in alluvial deposits. Gold is dense, soft, shiny and the most malleable and ductile pure metal known. Pure gold has a bright yellow color and luster traditionally considered attractive, which it maintains without rusting in air or water. It is one of the coinage metals and formed the basis for the gold standard used before the collapse of the Bretton Woods system in 1971.

Modern industrial uses include dentistry and electronics, where gold has traditionally found use because of its good resistance to oxidative corrosion. Chemically, gold is a transition metal and can form trivalent and univalent cations upon solvation. At STP it is attacked by aqua regia (a mixture of acids), forming chloroauric acid and by alkaline solutions of cyanide but not by single acids such as hydrochloric, nitric or sulfuric acids. Gold dissolves in mercury, forming amalgam alloys, but does not react with it. Gold is insoluble in nitric acid, which will dissolve silver and base metals, and is the basis of the gold refining technique known as "inquartation and parting". Nitric acid has long been used to confirm the presence of gold in items, and this is the origin of the colloquial term "acid test", referring to a gold standard test for genuine value