ChemSphere
79Au196.967

Gold

Transition metal · Period 6 · Group 11 · d-block

The metal that never tarnishes, coloured by relativity

Atomic mass
196.967 u
State at 25 °C
Solid
Electronegativity
2.54
Melting point
1,064.2 °C
Boiling point
2,969.9 °C
Configuration
[Xe] 4f14 5d10 6s1
Building atom…
79 protons 118 neutrons 79 electrons

Nucleus drawn at reduced count for clarity. Drag to rotate.

Gold, explained

Video lesson in production

Bhavya’s explainer for this element will play here.

Overview

Gold is the most malleable and among the least reactive of metals. Its configuration is [Xe]4f14 5d10 6s1, and its behaviour is shaped by Einstein's relativity. Gold's large nuclear charge makes inner electrons move at a substantial fraction of the speed of light, which contracts and stabilises the 6s orbital. The single 6s electron is therefore held unusually tightly, which helps explain why gold resists oxidation and why it can even form the auride ion, Au⁻, in compounds such as caesium auride.

The same effect narrows the energy gap between the filled 5d band and the 6s level, so gold absorbs blue light and reflects the yellow and red, giving it its colour. Silver, without such strong relativistic effects, absorbs only in the ultraviolet and looks white. Gold's resistance to corrosion and its excellent conductivity make it ideal for electrical contacts, while its inertness explains why it has been used for coins, jewellery and dental work for thousands of years.

Discovery

Gold has been known since prehistoric times because it occurs as native metal, in nuggets and river sands. The oldest worked gold yet found comes from the Varna Necropolis in Bulgaria, dated to about 4600–4200 BCE, and the kingdom of Lydia struck some of the first coins of gold alloy around 600 BCE. The English word comes from an old Germanic root meaning 'yellow', while the symbol Au comes from the Latin aurum.

Where it’s found
About 4 parts per billion of Earth's crust; it is mined as native gold in veins and placer deposits and extracted from low-grade ore by cyanide leaching.
What it’s used for
  • Jewellery
  • Bullion and coins
  • Electronic contacts
  • Dentistry
  • Spacecraft heat shielding
  • Nanoparticle medical diagnostics
In living things
No biological role. Metallic gold is inert and even edible as leaf; some gold compounds have been used to treat rheumatoid arthritis.
Safety
Metallic gold is safe; cyanide solutions used to extract it are extremely toxic.

How it compares

Where Gold sits among all 118 elements on the trends that shape the table.

  • Electronegativity2.54Pauling

    #12 of 100 elements with data

  • Ionization energy890kJ/mol

    #23 of 104 elements with data

  • Atomic radius135pm

    #59 of 95 elements with data

  • Electron affinity223kJ/mol

    #6 of 109 elements with data

  • Density19.3g/cm³

    #15 of 114 elements with data

  • Melting point1,340K

    #46 of 110 elements with data

Density
19.3 g/cm³
Atomic radius
135 pm
Covalent radius
124 pm
Molar heat
25.418 J/(mol·K)
Appearance
metallic yellow
Discovered by
Middle East

Inside the atom

79 electrons arranged in 6 shells: 2 · 8 · 18 · 32 · 18 · 1.

Orbital diagram

1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s1 4f14 5d10 · shorthand [Xe] 4f14 5d10 6s1

  1. 1s2
  2. 2s2
  3. 2p6
  4. 3s2
  5. 3p6
  6. 4s2
  7. 3d10
  8. 4p6
  9. 5s2
  10. 4d10
  11. 5p6
  12. 6s1
  13. 4f14
  14. 5d10

Each box is an orbital holding up to two electrons of opposite spin. Highlighted subshells hold the valence electrons that decide how Gold bonds.

Ionization energies

Energy to remove each electron in turn, on a log scale. Each electron is harder to remove than the last, because the remaining ones feel more of the nucleus.

Signature reactions

The chemistry Gold is known for.

  1. Redox · Complex formation

    Cyanide leaching

    Oxygen oxidises gold while cyanide ions bind the Au+ as the very stable dicyanoaurate complex, dissolving even microscopic gold particles from crushed ore. Most of the world's gold is extracted this way.

    4Au(s)+8NaCN(aq)+O2(g)+2H2O(l)4Na[Au(CN)2](aq)+4NaOH(aq)

    Conditions: dilute cyanide solution, air, pH above 10

  2. Redox · Complex formation

    Dissolving in aqua regia

    Nitric acid alone cannot oxidise gold, but chloride ions capture the Au3+ as the tetrachloroaurate ion, pulling the reaction forward. The result is a yellow solution of chloroauric acid.

    Au(s)+HNO3(aq)+4HCl(aq)HAuCl4(aq)+NO(g)+2H2O(l)

    Conditions: concentrated HCl and HNO3, about 3:1

  3. Redox · Single displacement

    Recovery with zinc

    Zinc, a more reactive metal, gives up electrons and takes over the cyanide ions, causing gold to precipitate as a fine dark powder. This Merrill–Crowe step recovers gold from leach solutions.

    2[Au(CN)2]−(aq)+Zn(s)2Au(s)+[Zn(CN)4]2−(aq)

    Conditions: zinc dust added to cyanide leach solution

Where you’ll meet it

  • Mask of Tutankhamun

    Mask of Tutankhamun

    This funerary mask contains about 10 kilograms of gold and still gleams after more than 3,300 years.

    Photo: Wikimedia Commons
  • Klondike Gold Rush

    Klondike Gold Rush

    Around 100,000 prospectors set out for Canada's Yukon after gold was found there in 1896.

    Photo: Wikimedia Commons
  • Voyager Golden Record

    Voyager Golden Record

    Gold-plated copper records carry sounds and images of Earth on the Voyager spacecraft.

    Photo: Wikimedia Commons
  • United States Bullion Depository

    United States Bullion Depository

    Fort Knox holds roughly 4,600 tonnes of the US government's gold reserves.

    Photo: Wikimedia Commons

Research

No research on Gold yet

When Bhavya publishes a project that studies Gold, it will be linked here.

See all research