Study Guides/Chemistry/Oxidation Number Rules
Study Guide · Chemistry

Oxidation Number Rules and Examples (O, N, S, C)

In Redox reactions, the Oxidation Number (or Oxidation State) represents the total number of electrons an atom gains or loses to form a chemical bond. Let's look at the rules for some key elements.

Question (Click to Flip)

What is the most common oxidation number of oxygen?

Answer

The most common oxidation number of oxygen in its compounds is -2. However, in peroxides, it is -1.

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Key Facts

Oxygen (O): Mostly -2 (except peroxides).

Nitrogen (N): Varies from -3 to +5.

Sulphur (S): Varies from -2 to +6.

Carbon (C): Varies from -4 to +4.

Oxidation Number of Oxygen (O)

Oxygen is highly electronegative.

  • General Rule: In almost all its compounds (like H₂O, CO₂), the oxidation number of Oxygen is -2.
  • Exceptions: In peroxides (like H₂O₂), it is -1. In the rare compound OF₂, it is +2.

Oxidation Number of Nitrogen (N)

Nitrogen is highly versatile and can exhibit many oxidation states.

  • Range: From -3 to +5.
  • Examples: In Ammonia (NH₃), N is -3. In Nitric acid (HNO₃), N is +5. In Nitrogen dioxide (NO₂), N is +4.

Oxidation Number of Sulphur (S)

Sulphur also shows multiple oxidation states.

  • Range: From -2 to +6.
  • Examples: In Hydrogen Sulphide (H₂S), S is -2. In Sulphur dioxide (SO₂), S is +4. In Sulphuric acid (H₂SO₄), S reaches its maximum of +6.

Oxidation Number of Carbon (C)

Carbon, being the king of organic chemistry, shows a wide range.

  • Range: From -4 to +4.
  • Examples: In Methane (CH₄), C is -4. In Carbon dioxide (CO₂), C is +4. In Carbon monoxide (CO), C is +2.

Questions and Answers

What is the most common oxidation number of oxygen?+

The most common oxidation number of oxygen in its compounds is -2. However, in peroxides, it is -1.

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