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Valency vs. Oxidation State: What's the Difference?

Edited by Aimie Carlson || By Harlon Moss || Updated on October 17, 2023
Valency refers to the combining capacity of an atom, while oxidation state indicates the degree of oxidation or reduction of an atom.

Key Differences

Valency is a fundamental concept rooted in the atom's ability to bond with other atoms. It essentially describes how many electrons an atom uses or needs to achieve a full outer shell. On the other hand, the oxidation state gives insight into an atom's electron distribution when considering the hypothetical transfer of electrons in bonds. It reveals how many electrons an atom has gained or lost.
Valency is primarily concerned with the actual chemical bonding in compounds. For instance, in water (H₂O), the valency of oxygen is 2 because it forms two bonds with hydrogen atoms. Oxidation state, conversely, considers the hypothetical charges on atoms. In the same molecule of water, the oxidation state of oxygen is -2, indicating it has a more negative character due to the electrons it shares with hydrogen.
While valency is often a fixed number for a given element in a specific compound, oxidation state can vary based on the element's surroundings and the other elements present. For instance, iron (Fe) can have oxidation states of +2 or +3 in different compounds. However, its valency in terms of bonding might remain consistent in those compounds.
In essence, valency is focused on an atom's bonding capacity, which can be physical and tangible in a molecule. Oxidation state is a theoretical concept, more about electron distribution and charge attribution.

Comparison Chart


Combining capacity of an atom.
Degree of oxidation or reduction of an atom.


Actual chemical bonds.
Hypothetical charges on atoms.

Numerical Value

Often whole numbers.
Can be whole, fractional, or zero.


Typically consistent for an element in a compound.
Can vary based on surroundings.

Relation to Electrons

Electrons needed or used for bonding.
Electrons gained or lost.

Valency and Oxidation State Definitions


The combining capacity of an atom.
The valency of hydrogen is 1.

Oxidation State

A theoretical charge an atom would have in a molecule or ion.
In NaCl, the oxidation state of sodium is +1.


A measure of an element's ability to bond with others.
Carbon has a valency of 4 because it can form four covalent bonds.

Oxidation State

Represents the effective charge of an atom in a compound.
In magnesium oxide, the oxidation state of magnesium is +2.


The number of electrons an atom can lose, gain, or share.
The valency of chlorine is 1, as it can gain one electron.

Oxidation State

The degree of oxidation or reduction of an atom.
The oxidation state of oxygen in H₂O is -2.


The total number of bonds an atom can form.
In methane, the valency of carbon is 4, forming four bonds with hydrogen.

Oxidation State

Indicates the electrons an atom gains, loses, or shares.
The oxidation state of iron in Fe₂O₃ is +3.


A descriptor of an atom's bond formation tendency.
The valency of oxygen in water is 2, indicating its two bonds with hydrogen.

Oxidation State

A concept used to describe electron distribution in compounds.
In sulfur hexafluoride, the oxidation state of sulfur is +6.


Variant of valence.


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How is valency determined?

Valency is determined by the number of electrons an atom can lose, gain, or share.

What is valency?

Valency is the combining capacity of an atom.

Are valency and oxidation state always the same?

No, while they can sometimes coincide, they often differ.

Why is valency important?

Valency helps predict how atoms will bond in compounds.

Can valency be zero?

Yes, for noble gases or molecules where an element doesn't form bonds, its valency is zero.

Is valency affected by the surrounding environment?

Valency is typically consistent for an element in a specific compound, regardless of surroundings.

Can oxidation state be fractional?

Yes, some elements can have fractional oxidation states.

What does a positive oxidation state indicate?

A positive oxidation state indicates a loss of electrons.

Is valency always a whole number?

Yes, valency is typically a whole number.

Do valency and oxidation state have any relation?

While both relate to electron interactions, valency deals with actual bonding and oxidation state with hypothetical charge distribution.

Can an element have multiple oxidation states?

Yes, elements, especially transition metals, can exhibit multiple oxidation states.

How does one calculate valency?

Valency is often deduced from the number of electrons needed to fill an atom's outer shell.

How does one determine the oxidation state in a complex ion?

Sum of oxidation states in a complex ion equals its charge.

What does oxidation state represent?

Oxidation state indicates the degree of oxidation or reduction of an atom.

How does valency relate to the periodic table?

Valency often corresponds to an element's group number, especially for main group elements.

Does every atom in a compound have a valency?

Yes, every atom has a valency, representing its bonding capacity.

Does a higher oxidation state mean an atom is more oxidized?

Yes, a higher positive oxidation state indicates a higher degree of oxidation.

How is oxidation state used in redox reactions?

Oxidation state helps determine which elements are oxidized and which are reduced.

What determines an atom's oxidation state in a compound?

The atom's electron distribution and its relationship with other atoms determine its oxidation state.

Can oxidation state be zero?

Yes, in elemental forms, the oxidation state is typically zero.
About Author
Written by
Harlon Moss
Harlon is a seasoned quality moderator and accomplished content writer for Difference Wiki. An alumnus of the prestigious University of California, he earned his degree in Computer Science. Leveraging his academic background, Harlon brings a meticulous and informed perspective to his work, ensuring content accuracy and excellence.
Edited by
Aimie Carlson
Aimie Carlson, holding a master's degree in English literature, is a fervent English language enthusiast. She lends her writing talents to Difference Wiki, a prominent website that specializes in comparisons, offering readers insightful analyses that both captivate and inform.

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