What are the most common oxidation states of gold?

Gold most commonly exhibits +1 (aurous, Au⁺) and +3 (auric, Au³⁺) oxidation states. Au(III) is the dominant state in aqueous chemistry and most gold compounds. Au(I) is prevalent in coordination compounds with soft Lewis-base ligands such as phosphines, thiolates, and cyanide.

Why can gold form a −1 oxidation state (auride)?

Relativistic contraction of the 6s orbital makes gold's electron affinity unusually high (222.8 kJ/mol) — higher than most transition metals and comparable to iodine. This allows gold to accept an electron and form Au⁻ (auride) in compounds with highly electropositive metals like caesium (CsAu). The −1 state is unique among transition metals at ambient conditions.

What is gold's electron configuration and why is it anomalous?

Gold's ground state is [Xe] 4f¹⁴ 5d¹⁰ 6s¹ rather than the expected 5d⁹ 6s². The filled 5d¹⁰ sub-shell is stabilised by relativistic effects: the 6s orbital contracts, lowering its energy so much that promoting one 5d electron into it is favourable. The same effect makes gold yellow (relativistic shift of absorption into the blue) and raises its melting point above platinum.

Why does Au(I) disproportionate but is still useful?

In water, Au(I) disproportionates to Au(0) and Au(III) because the standard potential E°(Au⁺/Au) > E°(Au³⁺/Au⁺). However, Au(I) is stable when coordinated by soft Lewis bases (phosphines, thiolates, CN⁻) that lower its reduction potential. Gold(I) chemistry is therefore carried out almost exclusively in coordination chemistry, not in simple aqueous salt solutions.

Does gold exhibit a +5 oxidation state?

Yes, but only in the powerful fluorinating agent gold(V) fluoride (AuF₅), formed by fluorination of gold metal at high temperature and pressure. AuF₅ is extremely reactive and of academic interest only. No +4 state is known for gold.

How do Au(I) and Au(III) differ in their coordination chemistry?

Au(I) is a d¹⁰ ion and strongly prefers two-coordinate linear geometry with soft σ-donor ligands. Au(III) is a d⁸ ion and strongly favours square-planar four-coordinate geometry, similar to Pt(II) and Pd(II). Both states show a pronounced affinity for soft donors (P, S, CN⁻) due to gold's relativistic-enhanced softness.

Gold Oxidation States

Name: Gold Oxidation States
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Author: Nham Vu

Reference for all known oxidation states of gold (Au): +1 and +3 are common; rarer states from −1 to +5 exist. Includes electron configuration and relativistic effects.

Atomic # 79 Au Gold

Atomic Mass

196.967 u

Group

11 (IB)

Period

Block

d-block

Electronegativity

2.54 (Pauling)

Oxidation States

+3, +1 (common)

Gold has a wider range of oxidation states than its Group 11 siblings (silver, copper), spanning −1 to +5. The +3 (auric) state dominates in aqueous chemistry and most compounds; +1 (aurous) is common in coordination chemistry with soft ligands. The rare −1 (auride) state arises from gold's relativistically enhanced electron affinity — unique among transition metals at ambient conditions.

State	Stability	Example	Notes
-1	Rare — auride compounds	CsAu	Relativistic 6s contraction makes Au electron affinity ~223 kJ/mol. Stable only with highly electropositive metals (Cs, Rb). CsAu is an ionic compound where gold acts as the anion.
0	Elemental only	Au(s)	Metallic gold. Exceptionally noble — does not oxidise in air or dissolve in single acids (only aqua regia or HCN/O₂).
+1	Stable with soft ligands	AuCN, AuCl	Aurous ion (Au⁺). Disproportionates in water to Au(0) + Au³⁺ but stabilised by soft donors: phosphines, thiolates, cyanide. Linear two-coordinate geometry (d¹⁰).
+2	Not isolable (disproportionates)	Au₂[PtF₆]	Au(II) would be d⁹ with an unpaired electron. Not isolable as a simple salt — disproportionates to Au(I) + Au(III). Found only in unusual bridged dimers with strong-field ligands.
+3	Stable — dominant state	AuCl₃, HAuCl₄	Auric ion (Au³⁺). Most stable state in aqueous media and most isolable compounds. Square-planar d⁸ geometry. Favoured by high hydration energy and stability of 5d⁸ configuration.
+5	Strongly oxidising	AuF₅	Known only as gold(V) fluoride — the most electron-withdrawing fluorinating agent of the platinum metals. Formed by direct fluorination of Au at high T and P. No +4 state is known for gold.

Relativistic effects — why gold is different from silver
Gold's 6s electron moves at ~58% of the speed of light, gaining relativistic mass and contracting its 6s orbital. This lowers 6s energy (raising electronegativity to 2.54 vs silver's 1.93), expands and destabilises 5d orbitals (narrowing the 5d→6s gap), and produces gold's characteristic yellow colour by shifting its optical absorption into the blue. The same contraction raises gold's electron affinity above that of most metals, enabling the unique −1 auride state.

Gold(I) compounds favour soft Lewis-base ligands and linear two-coordinate geometry. Gold(III) compounds are typically square-planar d⁸, structurally similar to platinum(II) and palladium(II) complexes. Gold is too noble to dissolve in simple acids; most synthetic gold compounds start from HAuCl₄ (chloroauric acid) dissolved in aqua regia.

Compound	Formula	Au State	Notes
Chloroauric acid	HAuCl₄	+3	The primary laboratory gold source. Formed by dissolving gold metal in aqua regia. Square-planar [AuCl₄]⁻ anion. Used to make gold nanoparticles and many other Au(III) compounds.
Gold(III) chloride	AuCl₃	+3	Reddish solid; actually a chloride-bridged dimer (Au₂Cl₆) with square-planar Au. Lewis acid; soluble in diethyl ether and alcohols.
Gold(III) oxide	Au₂O₃	+3	Metastable dark brown solid, decomposes above ~160 °C to Au metal and O₂. Reflects gold's nobility — the oxide is thermodynamically unstable at high temperature.
Gold(I) chloride	AuCl	+1	Yellow solid; stable when dry. Disproportionates in water to Au(0) + AuCl₃ unless stabilised by coordinating ligands.
Gold(I) cyanide	AuCN	+1	Linear Au–C≡N chain polymer. Used in gold electroplating baths. The cyanide ligand strongly stabilises Au(I) by σ-donation and π-backbonding.
Gold(I) thiosulfate	[Au(S₂O₃)₂]³⁻	+1	Key species in cyanide-free gold leaching (thiosulfate process). Thiolate and thioether ligands are soft donors that stabilise Au(I) effectively.
Chloro(triphenylphosphine)gold(I)	AuCl(PPh₃)	+1	Prototype homogeneous gold catalyst. Phosphine ligand stabilises the linear Au(I) centre; Au–P bond is exceptionally strong due to relativistic effects.
Caesium auride	CsAu	−1	Only isolable auride compound under ambient conditions. Ionic solid — Cs⁺ and Au⁻. Gold acts as the anion due to relativistic high electron affinity.
Sodium tetrachloroaurate(III)	NaAuCl₄	+3	Water-soluble gold(III) salt; used as a laboratory reagent, TEM staining agent, and in synthesis of gold nanoparticles.
Gold(V) fluoride	AuF₅	+5	Orange solid, extremely strong fluorinating agent. Synthesised only at high temperature and fluorine pressure. Reacts vigorously with water and most organic compounds.

Ground State Configuration

Core

Core (filled)

Core

Valence — anomalously full (relativistic)

Valence — singly occupied (relativistic contraction)

Notation

Noble gas: [Xe] 4f¹⁴ 5d¹⁰ 6s¹

Au⁺ (d¹⁰): [Xe] 4f¹⁴ 5d¹⁰

Au³⁺ (d⁸): [Xe] 4f¹⁴ 5d⁸

Ionization Steps

[Xe] 4f¹⁴ 5d¹⁰ 6s¹

Neutral atom — anomalous 5d¹⁰ 6s¹ (not 5d⁹ 6s²)

Au⁺

[Xe] 4f¹⁴ 5d¹⁰

Remove 6s¹ electron (IE₁ 890.1 kJ/mol) — d¹⁰, linear geometry

Au²⁺

[Xe] 4f¹⁴ 5d⁹

Remove one 5d electron (IE₂ ~1980 kJ/mol) — d⁹, unstable, disproportionates

Au³⁺

[Xe] 4f¹⁴ 5d⁸

Remove second 5d electron (IE₃ ~2940 kJ/mol) — d⁸, square-planar, stable

The anomalous 5d¹⁰ 6s¹ ground state
Simple aufbau predicts Au should be [Xe] 4f¹⁴ 5d⁹ 6s², yet it is 5d¹⁰ 6s¹. Relativistic contraction of the 6s orbital lowers its energy below the 5d, so the atom promotes one 5d electron into the lower-energy 6s to give the fully-filled 5d shell. The same effect makes gold's first ionization energy (890 kJ/mol) the highest of any transition metal — higher even than many nonmetals.

Why is gold yellow? The relativistic contraction narrows the 5d-to-6s energy gap so that it falls within the visible spectrum (~2.4 eV). Gold absorbs blue light (≈450 nm) via 5d→6s transitions and reflects red-yellow wavelengths, producing the characteristic gold colour. Silver's non-relativistic 5s orbital leaves a larger gap in the UV, so silver appears white. Copper's 3d→4s gap is close to gold's, giving copper its reddish tint — the only two non-grey transition metals owe their colour to the same effect.

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Summary

Reference for all known oxidation states of gold (Au): +1 and +3 are common; rarer states from −1 to +5 exist. Includes electron configuration and relativistic effects.

How it works

Click a tab — Oxidation States, Compounds, Electron Config, or Physical Props — to explore each topic.
The Oxidation States panel lists every known state from −1 to +5 with stability notes.
The Compounds panel shows representative Au(I) and Au(III) compounds with formulas and context.
The Electron Config panel covers the anomalous [Xe] 4f¹⁴ 5d¹⁰ 6s¹ ground state and relativistic contraction.
The Physical Props panel gives atomic and bulk data for quick reference.
Click any monospace table cell to copy its value to your clipboard.

Use cases

Students studying d-block transition metal chemistry and oxidation state trends.
Chemistry teachers explaining relativistic effects and gold's anomalous properties.
Researchers working with gold catalysis, AuNPs, or gold complexes needing quick compound data.
Jewellers and materials engineers needing context on Au(I)/Au(III) surface chemistry.
Anyone preparing for chemistry exams covering Group 11 or Period 6 elements.

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Last updated: 2026-07-23 · Reviewed by Nham Vu