Classification of oxides

• A binary compound of oxygen with another element is known as an oxide.
• There are various types of oxides. They are as follows:

A) Basic oxides:

• It is formed with alkali metals, alkaline earth metals (except Be) and transition metals generally.
• These oxides give bases with water.
• These oxides react with acids to form salt and water.
• For examples: Na₂O, K₂O, CaO, FeO, Pbo, etc.

Na₂O + H₂O → 2NaOH          Na₂O + 2HCl → 2NaCl + H₂O

B) Acidic oxides:

• Non-metals and transition metals in higher oxidation state (CO₂, SO₃, N₂O₅, V₂O₅, Mn₂O₇, CrO₃ ) form acidic oxides.
• These combine with water to give acid.
• These oxides react with bases to give salt and water.

CO₂ + H₂O  →    H₂CO₃           SO₂ + 2NaOH  →  Na₂SO₃ + H₂O

C) Amphoteric oxides:

• These are formed by amphoteric oxides.
• These react with both acids and bases.
• Examples: Al₂O₃, BeO, SnO, ZnO, etc.

Al₂O₃ + 6HCl →2AlCl₃ + 3H₂O

D) Neutral oxides:

• These neither give acids nor bases with water.
• For example: CO, H₂O, N₂O, NO, etc.

E) Normal oxides:

• In these oxides, oxygen content is as much as permitted by the normal valency of its metal.
• For examples: H₂O, Al₂O₃, etc.
• These contain only M-O bond.

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F) Poly- oxides:

• These oxides contain more oxygen than permitted by the normal valency of its metal.
• These are of various types. They are:

a) Peroxides: (with O-O linkage)

i)They give H₂O₂ with water or acid.

ii)In these oxides oxidation state of oxygen is -1.

iii)For example: BaO₂, Na₂O₂, etc.

b) Super-oxides:

i)Oxidation state of oxygen is -1/2.

ii)They contain O₂^2-.

iii)For examples: KO₂, RbO₂ and CsO₂.

 c) Dioxides:

i) Poly-oxides with higher percentage of oxygen.

ii)They do not yield H₂O₂ with water or acid.

iii)For example: MnO₂, PbO₂, etc.

G) Sub- oxides:

• Oxides containing less oxygen than permitted by normal valency of its metal are sub-oxides.
• For examples: N₂O, C₃O₂ (O=C=C=C=O).

H) Mixed oxides:

• These are the oxides made up of two similar oxides.
• For examples: red lead Pb₃O4 (2PbO + PbO₂) and ferroso-feric oxide/ loadstone Fe₃O₄ (FeO + Fe₂O₃)

References:

i) https://www.aakash.ac.in/important-concepts/chemistry/classification-of-oxides

ii) https://collegedunia.com/exams/classification-of-oxides-acidic-basic-amphoteric-and-neutral-oxides-articleid-5029

Classification of oxides