What is the most common oxidation state of molybdenum?

The +6 state is the most common and stable under ordinary conditions. It appears in molybdenum trioxide (MoO₃) and molybdate ions (MoO₄²⁻), the form Mo takes in soil and as a dietary trace element. The +4 state (MoS₂, MoO₂) is next most significant.

Why does molybdenum have so many oxidation states?

Molybdenum's ground-state configuration is [Kr] 4d⁵ 5s¹. The 4d and 5s electrons are close in energy and all accessible for bonding, allowing Mo to participate in oxidation states from -2 (in carbonyl clusters where d electrons back-donate into CO) all the way to +6 (losing all valence electrons). The high-spin half-filled 4d⁵ also confers extra stability at the +2 and +3 states.

What is the electron configuration of molybdenum?

The ground-state configuration is [Kr] 4d⁵ 5s¹ — not the expected [Kr] 4d⁴ 5s² — because a half-filled 4d subshell is more stable than a partially filled 4d with a doubly occupied 5s. Mo⁶⁺ has the configuration [Kr], Mo⁴⁺ is [Kr] 4d², and Mo²⁺ is [Kr] 4d⁴.

What are the most important molybdenum compounds industrially?

MoS₂ (molybdenite) is the primary ore and a solid lubricant. MoO₃ is the starting material for most Mo chemicals and a catalyst support. Ammonium molybdate ((NH₄)₂MoO₄) is used as a fertilizer additive and in analytical chemistry. Mo metal is used in high-temperature alloys for aerospace and tool steels.

What does the -2 oxidation state of molybdenum look like?

The -2 state appears in organometallic carbonyl complexes such as [Mo(CO)₄]²⁻ where the metal accepts electron density back from CO π* orbitals. These are not ionic compounds with Mo²⁻ ions but rather species where formal electron counting assigns -2 to the metal center. They are laboratory curiosities, not commercial compounds.

Is molybdenum a micronutrient?

Yes. Molybdenum is an essential trace element for most organisms. It is the active metal in nitrogenase (nitrogen fixation in bacteria) and xanthine oxidase (purine metabolism in mammals). The body requires only about 45 micrograms per day. It is absorbed as molybdate (MoO₄²⁻, Mo in the +6 state) from food and water.

Molybdenum Oxidation States

Name: Molybdenum Oxidation States
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Author: Nham Vu

Interactive reference for all molybdenum oxidation states (-2 to +6). Click a state to see compounds, colors, and notes. Includes electron configuration context and a compound lookup.

Atomic # 42 Mo Molybdenum

Atomic Mass

95.95 u

Group

6 (VIB)

Period

Block

d-block

Electronegativity

2.16 (Pauling)

Oxidation States

-2 to +6

Click any oxidation state to see its compounds, appearance, and chemistry. States marked Most common or Common are well-characterized under ordinary conditions.

Mo⁺⁶ Most common and stable [Kr] — all valence electrons removed

Mo(VI) is a d⁰ ion — all 4d and 5s electrons have been removed. It is the dominant oxidation state in nature and commerce. Molybdenum trioxide (MoO₃) is the main commercial form. In aqueous solution, Mo(VI) forms polymolybdate anions (Mo₇O₂₄⁶⁻, Mo₈O₂₆⁴⁻) at lower pH and the simple molybdate (MoO₄²⁻) in alkaline solution. Molybdate is the form absorbed by living organisms as a trace nutrient.

Formula	Name	Appearance	Notes
MoO₃	Molybdenum trioxide	White/pale yellow solid	Primary commercial Mo compound; catalyst support; ~90% of refined Mo passes through this form
MoO₄²⁻	Molybdate ion	Colorless in solution	Soluble form; micronutrient; corrosion inhibitor; agricultural fertilizer additive
(NH₄)₂MoO₄	Ammonium molybdate	White solid	Fertilizer additive; analytical reagent for phosphate detection (yellow molybdophosphate)
MoF₆	Molybdenum hexafluoride	Colorless liquid (bp 17 °C)	Used in CVD of Mo metal films; extremely reactive
H₂MoO₄	Molybdic acid	White solid	Acidic form of molybdate; used to make Mo salts
Mo₇O₂₄⁶⁻	Heptamolybdate (paramolybdate)	Colorless	Forms in slightly acidic molybdate solutions; common crystalline form as ammonium salt
CaMoO₄	Calcium molybdate	White solid	Scheelite structure; scintillator material; pigment
Na₂MoO₄·2H₂O	Sodium molybdate dihydrate	White solid	Industrial corrosion inhibitor; fertilizer; catalyst

All well-characterized molybdenum compounds, sorted by oxidation state. Click any formula cell to copy it.

Formula	Name	Mo State	Appearance	Key Use
Mo(CO)₄]²⁻	Tetracarbonylmolybdate	-2	Colorless solution	Organometallic research
[Mo(CO)₅]⁻	Pentacarbonylmolybdate	-1	Colorless	Cluster precursor
Mo(CO)₆	Molybdenum hexacarbonyl	0	White crystals	CVD precursor, lab reagent
Mo (metal)	Molybdenum	0	Silvery-white solid	Alloy steels, electrodes
MoCl₂	Molybdenum(II) chloride	+2	Yellow solid (cluster)	Synthesis precursor
[Mo₆Cl₈]⁴⁺	Hexamolybdenum cluster	+2	Yellow	Photoluminescent research
MoCl₃	Molybdenum(III) chloride	+3	Dark red-brown	Organometallic precursor
[Mo(CN)₈]⁵⁻	Octacyanomolybdate(III)	+3	Orange solution	Electron-transfer studies
MoS₂	Molybdenum disulfide	+4	Black, layered	Dry lubricant, 2D material, primary ore
MoO₂	Molybdenum dioxide	+4	Violet-brown	Electrode material, catalyst
MoCl₄	Molybdenum(IV) chloride	+4	Black solid	Lewis acid, precursor
MoSe₂	Molybdenum diselenide	+4	Gray-black, layered	Photovoltaics, lubricant
MoTe₂	Molybdenum ditelluride	+4	Black, layered	2D semiconductor research
MoCl₅	Molybdenum(V) chloride	+5	Dark green solid	Olefin metathesis catalyst
Mo₂O₅	Dimolybdenum pentoxide	+5	Black solid	Mixed-valence intermediate
MoO₃	Molybdenum trioxide	+6	White/pale yellow	Primary commercial form, catalyst support
MoF₆	Molybdenum hexafluoride	+6	Colorless liquid	CVD Mo metal films
H₂MoO₄	Molybdic acid	+6	White solid	Mo salt precursor
(NH₄)₂MoO₄	Ammonium molybdate	+6	White solid	Fertilizer, analytical reagent
Na₂MoO₄	Sodium molybdate	+6	White solid	Corrosion inhibitor, fertilizer
CaMoO₄	Calcium molybdate	+6	White solid	Scintillator, pigment
PbMoO₄	Lead molybdate (wulfenite)	+6	Yellow-orange mineral	Mineral; historically pigment
Mo₇O₂₄⁶⁻	Heptamolybdate	+6	Colorless	Low-pH molybdate polyoxoanion
MoO₄²⁻	Molybdate ion	+6	Colorless in solution	Micronutrient, corrosion inhibitor

Ground State Configuration

Notation

Full: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d⁵ 5s¹

Noble gas: [Kr] 4d⁵ 5s¹

Note: expected [Kr] 4d⁴ 5s² — but the half-filled 4d⁵ with 5s¹ is lower energy due to exchange-energy stabilization of the half-filled d subshell.

Valence Orbital Diagram

Half-filled — 5 unpaired electrons → +2 to +6 oxidation states by progressive removal

Singly occupied — first electron removed (IE₁). Anomalous: expected 2 electrons here.

Electron Count by Oxidation State

[Kr] 4d⁵ 5s¹

d⁵ s¹ — neutral, half-filled d, anomalous s¹

Mo⁺

[Kr] 4d⁵

d⁵ — stable half-filled d after 5s¹ removal

Mo²⁺

[Kr] 4d⁴

d⁴ — loses one d electron next

Mo³⁺

[Kr] 4d³

d³ — isoelectronic with Cr³⁺; paramagnetic

Mo⁴⁺

[Kr] 4d²

d² — MoS₂, MoO₂; common in solid-state chemistry

Mo⁵⁺

[Kr] 4d¹

d¹ — MoCl₅; paramagnetic (one unpaired electron)

Mo⁶⁺

[Kr]

d⁰ — diamagnetic; all valence electrons removed; MoO₃

Why Mo adopts so many states
The 4d and 5s orbitals in molybdenum are close in energy. All six valence electrons (4d⁵ 5s¹) are accessible for bonding, enabling Mo to range from -2 (back-donation in carbonyls) to +6 (full d⁰ in MoO₃). The half-filled 4d⁵ at the Mo⁺ stage also provides extra exchange-energy stabilization, making +1 and +2 cluster compounds more accessible than in neighboring elements.

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Summary

Interactive reference for all molybdenum oxidation states (-2 to +6). Click a state to see compounds, colors, and notes. Includes electron configuration context and a compound lookup.

How it works

Click any oxidation state card in the explorer grid to load its details — compounds, appearance, and chemistry notes.
The highlighted cards (+6 and +4) mark the most stable and industrially important states.
Use the Compound Finder to search by formula (e.g., MoO3, MoS2) and see the Mo oxidation state within it.
The Electron Config tab shows the [Kr] 4d⁵ 5s¹ ground state, orbital diagram, and ionization context.
The Compounds tab lists all cataloged Mo compounds with their formula, Mo state, color, and use.

Use cases

Students studying d-block transition metal chemistry and variable oxidation states.
Chemistry teachers preparing material on Period 5 or Group 6 elements.
Industrial chemists working with Mo catalysts (hydrodesulfurization, ammonia synthesis).
Materials scientists selecting Mo compounds for coatings or lubricants (MoS₂).
Exam preparation for questions on transition metal electron configurations and redox chemistry.

Frequently Asked Questions

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