What are the common oxidation states of vanadium?

Vanadium most commonly exhibits +2, +3, +4, and +5 oxidation states. The +5 state (VO4³⁻, VO2⁺) and +4 state (VO²⁺ vanadyl) are the most stable under ambient conditions. The +2 and +3 states are reducing agents and less stable in air.

What color is each vanadium oxidation state in solution?

V²⁺ is violet, V³⁺ is green, V⁴⁺ (as VO²⁺) is blue, and V⁵⁺ (as VO2⁺) is yellow. This rainbow progression is used in teaching labs to demonstrate stepwise reduction of ammonium metavanadate with zinc in acid.

What is the electron configuration of vanadium?

Neutral vanadium is [Ar] 3d³ 4s². In the +2 state it is [Ar] 3d³, in +3 it is [Ar] 3d², in +4 it is [Ar] 3d¹, and in +5 it is [Ar] (no d-electrons remain). The progressive loss of 3d electrons is responsible for the changing colors.

Why does vanadium have so many oxidation states?

As a transition metal, vanadium has partially filled 3d orbitals (3d³ 4s² ground state). The 3d and 4s electrons are close in energy, making it relatively easy to remove multiple electrons and access several stable oxidation states.

What is the most stable oxidation state of vanadium?

The +5 state in the form of vanadate (VO4³⁻) or dioxovanadium(V) (VO2⁺) is the most thermodynamically stable in oxidizing, acidic conditions. In air at ambient temperature, vanadium compounds tend to oxidize toward +5.

What is vanadium pentoxide used for?

Vanadium pentoxide (V₂O₅) is the catalyst in the contact process for manufacturing sulfuric acid, where it cycles between the +5 and +4 states. It is also used in glass manufacturing and as a precursor to other vanadium compounds.

Vanadium Oxidation States

Name: Vanadium Oxidation States
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Author: Nham Vu

Reference for vanadium's four common oxidation states (+2 to +5), their aqueous solution colors, electron configurations, and key compounds.

Atomic # 23 V Vanadium

Atomic Mass

50.9415 u

Group

5 (VB)

Period

Block

d-block

Electronegativity

1.63 (Pauling)

Oxidation States

+2, +3, +4, +5

Vanadium is one of the few elements with four accessible oxidation states under ordinary laboratory conditions. Each state has a characteristic color in aqueous solution, making vanadium a classic subject in transition metal chemistry demonstrations.

State	Species (acid)	Color	d-electrons	Stability
+2	V²⁺	Violet	3d³	Strong reducing agent; oxidizes readily in air
+3	V³⁺	Green	3d²	Reducing agent; stable under inert atmosphere
+4	VO²⁺	Blue	3d¹	Stable vanadyl ion; common in solution
+5	VO₂⁺	Yellow/Orange	3d⁰	Most oxidized; thermodynamically stable in air

Electron configuration (neutral V): [Ar] 3d³ 4s²
The 4s electrons are removed first on ionization; subsequent 3d electrons are removed for higher states.

V²⁺

Violet

Oxidation State

Aqueous Species

V²⁺

Solution Color

Violet

Electron Config

[Ar] 3d³

d-electron Count

Spin State

³⁄₂ (3 unpaired e⁻)

V²⁺ is a strong reducing agent and is rapidly oxidized by oxygen in air to V³⁺ or higher states. It is formed by reduction of higher vanadium states with zinc metal in dilute sulfuric acid. The violet color arises from d-d electronic transitions in the octahedral [V(H₂O)₆]²⁺ complex.

Key Compounds

Compound	Formula	Notes
Vanadium(II) Chloride	VCl₂	Pale violet solid; strong reducing agent; absorbs O₂ from air.
Vanadium(II) Sulfate	VSO₄	Forms violet hydrate [V(H₂O)₆]SO₄ in solution.
Vanadium(II) Oxide	VO	Black solid; NaCl-type structure; metallic conductivity.
Hexaaquavanadium(II)	[V(H₂O)₆]²⁺	Characteristic violet aqueous ion; highly reducing.

V³⁺

Green

Oxidation State

Aqueous Species

V³⁺

Solution Color

Green

Electron Config

[Ar] 3d²

d-electron Count

Spin State

1 (2 unpaired e⁻)

V³⁺ is a moderate reducing agent, more stable than V²⁺ but still susceptible to oxidation by air. The green color of [V(H₂O)₆]³⁺ is due to d-d transitions with two 3d electrons in an octahedral field. V³⁺ is an intermediate species in the stepwise reduction of vanadate used in laboratory demonstrations.

Key Compounds

Compound	Formula	Notes
Vanadium(III) Chloride	VCl₃	Green-violet solid; Lewis acid; used as polymerization catalyst (Ziegler-Natta).
Vanadium(III) Oxide	V₂O₃	Black solid; undergoes metal-insulator transition at ~155 K.
Vanadium(III) Sulfate	V₂(SO₄)₃	Green salt; used in electroplating baths.
Hexaaquavanadium(III)	[V(H₂O)₆]³⁺	Green aqueous ion; hydrolyzes in dilute base.

VO²⁺

Blue

Oxidation State

Aqueous Species

VO²⁺ (vanadyl)

Solution Color

Blue

Electron Config

[Ar] 3d¹

d-electron Count

Spin State

½ (1 unpaired e⁻)

The +4 state exists predominantly as the vanadyl ion (VO²⁺), a stable oxo-cation with a strong V=O double bond. It is blue in aqueous solution. Vanadyl compounds are used in diabetes research, catalysis, and as EPR spectroscopy spin probes due to the single unpaired d-electron. Vanadyl sulfate (VOSO₄) is a common supplement sold as an insulin mimetic.

Key Compounds

Compound	Formula	Notes
Vanadyl Sulfate	VOSO₄	Blue solid; most common V(IV) salt; used as supplement and catalyst precursor.
Vanadium Dioxide	VO₂	Black solid; remarkable metal-insulator transition at 68 °C; used in smart windows.
Vanadyl Chloride	VOCl₂	Blue-green solid; hydrolyzes in moist air.
Vanadyl Acetylacetonate	VO(acac)₂	Blue-green powder; widely used EPR spin probe and catalyst.

VO₂⁺

Yellow

Oxidation State

Aqueous Species

VO₂⁺ (dioxovanadium)

Solution Color

Yellow / Orange

Electron Config

[Ar] (3d⁰)

d-electron Count

Spin State

0 (diamagnetic)

The +5 state is vanadium's highest common oxidation state and is the most stable in air. In acidic solution it exists as dioxovanadium(V) VO₂⁺ (yellow); in alkaline solution it forms vanadate VO₄³⁻ (colorless to pale yellow). V₂O₅ is the industrially critical catalyst in the contact process for sulfuric acid synthesis, cycling between +5 and +4. Because V(V) has no d-electrons, it is diamagnetic and its color stems from charge-transfer transitions rather than d-d transitions.

Key Compounds

Compound	Formula	Notes
Vanadium Pentoxide	V₂O₅	Orange-red solid; main industrial vanadium compound; catalyst for H₂SO₄ production.
Ammonium Metavanadate	NH₄VO₃	White/pale yellow salt; precursor for V₂O₅; used in chemical demonstrations.
Sodium Vanadate	NaVO₃	White solid; used as a phosphatase inhibitor in biochemistry.
Vanadyl Trichloride	VOCl₃	Yellow liquid; Lewis acid; used in Ziegler-Natta catalyst systems.

The four oxidation states of vanadium are interconverted by one-electron redox steps. Standard reduction potentials are given for aqueous acid (pH 0). More positive E° means the oxidized form is a stronger oxidant.

VO₂⁺

Oxidation State +5

VO₂⁺ + 2H⁺ + e⁻ → VO²⁺ + H₂O

E°

+1.00 V

VO²⁺

Oxidation State +4

VO²⁺ + 2H⁺ + e⁻ → V³⁺ + H₂O

E°

+0.36 V

V³⁺

Oxidation State +3

V³⁺ + e⁻ → V²⁺

E°

−0.26 V

V²⁺

Oxidation State +2

V²⁺ + 2e⁻ → V(s)

E°

−1.13 V

Half-Reaction	E° (V vs SHE)	Note
VO₂⁺ + 2H⁺ + e⁻ → VO²⁺ + H₂O	+1.00	V/V couple used in positive half-cell of vanadium redox battery (VRFB)
VO²⁺ + 2H⁺ + e⁻ → V³⁺ + H₂O	+0.36	Moderate oxidant; relevant in analytical oxidimetry
V³⁺ + e⁻ → V²⁺	−0.26	V(III)/V(II) couple; used in negative half-cell of VRFB
V²⁺ + 2e⁻ → V(s)	−1.13	Reference for metallic vanadium deposition

Vanadium Redox Flow Battery (VRFB):
VRFBs exploit the V(II)/V(III) couple at the negative electrode and the V(IV)/V(V) couple at the positive electrode, giving a cell voltage of ~1.26 V. All four oxidation states coexist in the same electrolyte (H₂SO₄ solution), eliminating cross-contamination from mixing.

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Summary

Reference for vanadium's four common oxidation states (+2 to +5), their aqueous solution colors, electron configurations, and key compounds.

How it works

Select an oxidation state tab (+2, +3, +4, or +5) to view its properties.
The color swatch shows the characteristic aqueous solution color for that state.
The electron configuration panel shows which d-electrons remain after ionization.
The compounds table lists key examples and their use cases.
The Redox Ladder tab shows how the four states interconvert and their standard potentials.
Click any cell in the compounds table to copy its text to your clipboard.

Use cases

Students studying transition metal chemistry and d-block oxidation state trends.
Chemistry teachers preparing demonstrations on solution color changes with vanadium.
Researchers working with vanadium redox flow battery (VRFB) electrolytes.
Analysts using vanadium titrations or colorimetric assays in the lab.
Engineers designing vanadium catalysts for sulfuric acid production (V2O5 contact process).
Anyone preparing for chemistry exams covering transition metal oxidation states.

Frequently Asked Questions

Last updated: 2026-07-08 · Reviewed by Nham Vu