Gold (Au)
Gold (Au) is a transition metal with atomic number 79 and a standard atomic weight of 196.97. At room temperature it is a solid that melts at 1,064 °C and boils at 2,836 °C.
Gold key facts
Gold at a glance
Identity
| Symbol | Au |
|---|---|
| Atomic number (Z) | 79 |
| Atomic weight | 196.97 ± 0.01 (CIAAW 2024) |
| Category | Transition metal |
| Group | 11 |
| Period | 6 |
| Block | d-block |
| CAS number | 7440-57-5 |
Atomic properties
| Electron configuration | [Xe] 4f14 5d10 6s1 Full: 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f14 5s2 5p6 5d10 6s1 |
|---|---|
| Electrons per shell | 2, 8, 18, 32, 18, 1 |
| Oxidation states | +3 Less common: -3, -2, -1, 0, +1, +2, +5 |
| Electronegativity (Pauling) | 2.54 |
| First ionisation energy | 9.226 eV (890.1 kJ/mol) 2nd: 20.203 eV · 3rd: 30 eV |
| Electron affinity | 2.309 eV |
| Atomic radius (empirical) | 135 pm |
| Covalent radius | 124 pm |
| Van der Waals radius | 214 pm |
Physical properties
| State at 25 °C | Solid |
|---|---|
| Melting point | 1,064.2 °C · 1,947.5 °F · 1,337.33 K |
| Boiling point | 2,836 °C · 5,136.8 °F · 3,109.15 K |
| Density | 19.3 g/cm³ |
| Specific heat capacity | 0.129 J/(g·K) |
| Thermal conductivity | 318 W/(m·K) |
| Crystal structure | Face-centred cubic |
Isotopes & abundance
| Natural occurrence | Primordial |
|---|---|
| Radioactive | No |
| Natural isotopes (abundance) | 197Au 100% |
| Stable isotopes | 2 |
| Known isotopes | 43 |
| Abundance in Earth's crust | 0.004 mg/kg |
| Abundance in seawater | 0.000004 mg/L |
Atomic weights: CIAAW Abridged Standard Atomic Weights 2024. Other properties: standard reference compilations, checked October 2026; predicted values are marked.
Gold electron configuration
Gold has 79 electrons. Written in short form, its ground-state configuration is [Xe] 4f14 5d10 6s1 — the electrons of the noble gas xenon, plus 4f14 5d10 6s1.Written out in full: 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f14 5s2 5p6 5d10 6s1.
An exception to the filling rule. The simple aufbau (Madelung) order predicts 6s2, 5d9, but gold actually has 6s1, 5d10. Half-filled and filled subshells, and the close energies of the outer orbitals, make this arrangement more stable.
Discovery and name
Prehistoric — Known since antiquity.
Anglo-Saxon gold; the symbol Au is from Latin aurum.
Known for
Prized since prehistory; does not tarnish. Used in jewellery, investment, electronics connectors and dentistry. Very malleable — it can be beaten into leaf 0.1 µm thick.
Isotopes of gold
Naturally occurring gold is a mix of 1 isotope. Each has 79 protons; they differ in the number of neutrons:
| Isotope | Protons | Neutrons | Natural abundance | Stability |
|---|---|---|---|---|
| 197Au | 79 | 118 | 100% | stable |
43 isotopes of gold are known in our data set (half-lives as published in nuclear data tables).
Gold compared with group 11
The other elements in group 11, from top to bottom of the table:
| Element | Z | Atomic weight | Melting point | Boiling point | Density | Electronegativity |
|---|---|---|---|---|---|---|
| Copper | 29 | 63.546 | 1,085 °C | 2,560 °C | 8.96 g/cm³ | 1.9 |
| Silver | 47 | 107.87 | 962 °C | 2,162 °C | 10.5 g/cm³ | 1.93 |
| Gold | 79 | 196.97 | 1,064 °C | 2,836 °C | 19.3 g/cm³ | 2.54 |
| Roentgenium | 111 | [282] | — | — | 28.7 g/cm³ (pred.) | — |