Hey chemistry enthusiasts! I’m Inam Jazbi, and today we’re diving into the world of oxides – from the simple ones like water and carbon monoxide to the unusual ones like peroxides and suboxides. In this guide, I’ll break everything down with examples, properties, and uses so you can cram smartly for MDCAT or just enjoy chemistry in a fun, easy way. Let’s uncover the secrets of oxides together! 🧪💡

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Oxides and Its Types

Definition of Oxides

Oxides are the binary compounds of oxygen with other elements i.e. with metals, non-metals and metalloids e.g. Na₂O, Al₂O₃, Na₂O₂, KO₂, NO, CO₂ etc.

Oxides Uncovered: Types, Properties & Uses

Oxides are also termed as Anhydrides

Oxides are also termed as anhydrides as they are considered to be formed from respective acid or base by the loss of water molecule.

Acid-Base Nature of Oxides

🟢Oxides of metals → basic

🟢Oxides of non-metals → acidic or neutral

🟢 Oxides of metalloids or amphoteric metals → amphoteric in nature.

Nature of Oxides and Oxidation State

The oxidation state of the metal affect the acid or base character of its oxide. The acidity increases with increasing oxidation state. e.g. MnO (+2) < Mn₂O₃ (+3) < MnO₂ (+4) < Mn₂O₇ (+7)

Classification of Oxides based on Bonding Type

💥Ionic Oxides

💥 Covalent Oxides

Classification of Oxides based on Oxidation State of Oxygen

💥Normal Oxides → Oxidation state of O = −2 Contain oxide, O²⁻ ion e.g. Na₂O, CaO, SrO etc.

💥Peroxides Oxides → Oxidation state of O = −1 Contain peroxide, O₂²⁻ ion e.g. Na₂O₂, SrO₂, BaO₂, H₂O₂ etc.

💥Superoxides → Oxidation state of O = −½ Contain superoxide, O₂¹⁻ ion e.g. KO₂, RbO₂, CsO₂ etc.

💥Suboxides → Oxidation state of O = −2 Contain oxide, O²⁻ ion with less oxygen e.g. C₃O₂ etc.

Classification of Oxides Based on their Acid-Base Properties

🔵Basic Oxides (Oxides of metals e.g. Na₂O, CaO, SrO etc.)

🔵Acidic Oxides (Oxides of non-metals e.g. CO₂, SO₂, NO₂, Cl₂O etc.)

🔵Amphoteric Oxides (Oxides of amphoteric metals e.g. BeO, ZnO, Al₂O₃, PbO, PbO₂, SnO, SnO₂ etc.)

🔵Neutral Oxides (Oxides of less reactive non-metals e.g. H₂O, N₂O, NO, CO)

1. Peroxides

Peroxides are oxides in which oxygen has an oxidation state of oxygen of –1 instead of –2 in most oxides) containing peroxide ion (O₂²⁻) with an O–O single bond (peroxide linkage) having higher proportion of oxygen as compared to normal oxides.

Examples

Hydrogen peroxide (H₂O₂), Sodium peroxide (Na₂O₂), Strontium peroxide (SrO₂), Barium peroxide (BaO₂).

Important Points / Tips

⚡O–O bond is weak, so peroxides are strong oxidizers and unstable.

⚡Hydrogen peroxide is both oxidizing and reducing agent depending on reaction.

⚡Concentrated H₂O₂ is explosive, keep in dark bottles.

⚡Organic peroxides are used in industry but are dangerous due to instability.

⚡ They produce hydrogen peroxide with acids or water. Na₂O₂ + 2HCl → H₂O₂ + 2NaCl

2. Superoxides

Superoxides are oxides in which oxygen has an oxidation state of – ½ or –0.5 containing superoxide ion (O₂¹⁻) having more oxygen than peroxides.

Examples

Potassium superoxide(KO₂), Rubidium superoxide (RbO₂), Cesium superoxide (CsO₂).

Important Points / Tips

⚡Superoxides are more reactive than peroxides.

⚡Oxygen in superoxides has oxidation state -½, peroxide -1.

⚡Alkali metals form superoxides with heavier metals (K, Rb, Cs), not Li.

⚡KO₂ is yellow-orange solid, soluble in water, releases O₂ slowly.

3. Suboxides

Suboxides are oxides containing oxide ion (O²⁻) in which oxygen has an oxidation state of –2 having less amount of oxygen than the normal oxides.

Examples

Carbon suboxide, C₃O₂, Copper Suboxide: Cu₂O, Gold Suboxide: Au₂O₃ (less common), Cesium Suboxide: Cs₁₁O₃

4. Normal Oxides

Definition

Normal oxides are those oxides containing oxide ion (O²⁻) in which oxygen shows its normal oxidation state (valency number) of –2.

Examples

Li₂O, Na₂O, MgO, BaO, CO₂, SO₂, H₂O, N₂O, etc.

Four Kinds of Normal Oxides on the basis of their chemical characteristics and acid-base behaviour

(a) Neutral oxides

The oxides which in contact with water produce neither an acid nor a base and are neutral to litmus are called neutral oxides.

Examples

Carbon monoxide (CO), Nitric oxide (NO), Nitrogen oxide (N₂O), Hydrogen oxide (H₂O).

(b) Amphoteric Oxides

Oxides of certain less electropositive Amphoteric metals (Be, Al, Ga, In, Ge, Sn, Pb, Zn, Cr etc.) and some metalloids (like As, Sb, Te etc.) which are insoluble in water which possess dual properties of acidic as well as basic oxides having ability to react with both acid and base are called amphoteric oxides. (The oxides of Pb, Sn, Ge and in lower oxidation states are basic).

Examples

Al₂O₃, ZnO etc.

Preparation by Direct Union of less electropositive metals with Oxygen on Heating

2Zn + O₂ → 2ZnO

4Al + 3O₂ → 2Al₂O₃

Properties

They behave as acid with bases and act as base with acids i.e. they react with both acids and bases to form salt and water.

ZnO(s) + 2HCl(aq) → ZnCl₂(aq) + H₂O(l)

ZnO(s) + 2NaOH(aq) → Na₂ZnO₂(aq) + H₂O(l)

Al₂O₃(s) + 2NaOH(aq) → 2NaAlO₂(aq) + H₂O(l)

Al₂O₃(s) + 6HCl(aq) → 2AlCl₃(aq) + 3H₂O(l)

(c) Basic Oxide

The normal oxides of metals which readily dissolves in water to produce their respective soluble metal hydroxide producing alkaline solution turning red litmus blue are called basic or metallic oxides. However, certain amphoteric metals form amphoteric oxides.

Examples

Li₂O, Na₂O, K₂O, MgO, CaO, etc.

Preparation by Direct Union of Metal with Oxygen on Heating

4Na + O₂→ 2Na₂O

2Ca + O₂ → 2CaO

Properties

1. Most basic oxides are soluble in water and react with water to yield their hydroxides and turn red litmus blue.Na₂O(s)+ H₂O(l) → 2NaOH(aq)

K₂O(s) + H₂O(l) → 2KOH(aq)

CaO(s) + H₂O(l) → Ca(OH)₂(aq)

MgO(s) + H₂O(l) → Mg(OH)₂(s)

2. They being basic neutralize with acids to produce salt and water.

Na₂O + 2HCl → 2NaCl + H₂O

MgO + 2HCl → MgCl₂ + H₂O

(d) Acidic Oxides

The normal oxides of non-metals which readily dissolves in water to produce their respective oxyacids producing acidic solution and turn blue litmus red are called acidic or non-metallic oxides.

Examples

CO₂, SO₂, SO₃, P₂O₅ etc.

Preparation

C + O₂ → CO₂

S + O₂ → SO₂

Properties

1. Most acidic oxides are soluble in water and react with water to yield their oxyacids and turn blue litmus red.

CO₂(g) + H₂O(l) → H₂CO₃ (aq) (Carbonic Acid)

SO₂(g) + H₂O(l) → H₂SO₃ (aq) (Sulphurous Acid)

P₂O₅(g) + H₂O(l) → 2H₃PO₄(aq) (Phosphoric Acid)

2. They produce salt and water on reaction with bases.

CO₂ + 2NaOH→ Na₂CO₃ + H₂O

SO₃ + 2NaOH → Na₂SO₄ + H₂O

🌟📘Acid-Base Behaviour of Oxides

🔥 Al₂O₃ does not react with dilute acids and dilute alkali.

🔥 Al₂O₃ dissolves in alkali to form soluble aluminate ion

🔥Al₂O₃ + 2OH⁻ + 3H₂O → 2[Al(OH)₄]⁻ (aluminate ion or tetrahydroxyaluminate(III) ion)

🔥Al₂O₃ dissolves in acids to form soluble aluminium ions (salts).

🔥 Al₂O₃ + 6H⁺ → 2Al³⁺ + 3H₂O

🔥 SiO₂ does not react with water.

🔥SiO₂ reacts with concentrated alkalis forming silicates (SiO₃²⁻).

🔥 NO₂ reacts with water forming two oxyacids HNO₂ and HNO₃.

🔥 The oxides of P, S and Cl except ClO₂ react readily with water to form strongly acidic solution.

🔥 HClO₄ is called perchloric acid.

🌟📘Reaction of Oxides with water, acids and alkalis

🔥 Metal oxides are ionic and form basic solution.

🔥 Non-metallic oxides are covalent and form acidic solution.

🔥 Normal oxides of most metals being basic combine with acids to form salts and water.

🔥 Normal oxides of most non-metals being acidic combine with alkalis to form salts and water.

🔥 Basic metallic oxides dissolve in water to form soluble hydroxides (alkalis).

🌟📘Mixed Anhydrides OR Double Anhydrides

Mixed anhydrides are the non-metallic oxides that react with water to form a mixture of two oxyacids containing the non-metallic elements in two different oxidation states. Oxidation state of nonmetal in one acid should be higher than oxidation state of same in the anhydride form and another acid should have less oxidation state than anhydride). The common mixed anhydrides include NO₂, ClO₂ and Cl₂O₆, As₂O₃.

2NO₂ + H₂O → HNO₂ + HNO₃

2ClO₂ + H₂O → HClO₂ + HClO₃

Cl₂O₆ + H₂O → HClO₃ + HClO₄

As₂O₃ + H₂O → H₃AsO₃+ H₃AsO₄

🌟📘Mixed Oxides

Mixed oxides are the oxides containing oxide anion (O²⁻) along with cations of two or more chemical element or cations of single element in several oxidation states. Mixed oxides are intermediate between a metal oxide and a metal salt.

Examples

(i) Magnetite/ferrosoferric oxide Fe₃O₄, contains Fe²⁺ (ferrous) and Fe³⁺ (ferric) cations in 1:2 ratio.

(ii) Red lead; Pb₃O₄

(iii) Strontium titanate SrTiO₃

(iv) Ilmenite (FeTiO₃), a mixed oxide of iron (Fe²⁺) and titanium (Ti⁴⁺) cations.

(v) Perovskite is calcium titanium oxide mineral composed of calcium titanate (CaTiO₃)

(vi) Yttrium aluminium garnet Y₃Al₅O₁₂

Criteria of Deciding Strength of Oxides

Basic Strength

The basic strength of oxides increases on descending each group while decreases across each period from left to right. Thus last congener of each group always forms basic oxide. The increasing strength of basic character of oxides on descending each group is attributed to increasing electropositivity. Greater the electropositivity of an element, stronger is the basic strength of oxides. In a given period, the oxides progress from strongly basic through weakly basic, amphoteric and weakly acidic to strongly acidic.

The basicity of main group metal oxides increases on descending a group of the periodic table e.g.
BeO < MgO < CaO < SrO < BaO
The basicity of transition metal oxides (Sub group B) decreases from top to bottom.

Acidic Strength

The acidic strength of oxides increases across each a period from left to right while decreases on descending each group. Thus last member of each Period is liable to form acidic oxide. The increasing strength of acidic oxides across each period is due to increasing electronegativity. Greater the electronegativity of an element, stronger is the acidic character of oxides.

🌟🧪 Oxides & Its Types – Mega Revision Sheet by Inam Jazbi

🔹 1. Definition

🟢 Oxides: Compounds of oxygen with another element.
🟡 Oxygen usually has oxidation state -2, except in peroxides (-1) and superoxides (-½).
🔵 General formula varies:
⚡Normal oxides → MO, M₂O₃
⚡Peroxides → H₂O₂, Na₂O₂
⚡Superoxides → KO₂, NaO₂
⚡Suboxides → Cu₂O, Cs₁₁O₃

🔹 2. Types of Oxides with Examples

Type	Examples	Oxygen Oxidation State	Hint / Use
🟠 Normal Oxide	CO, CuO	-2	Common oxides, basic, acidic, or amphoteric
🟣 Peroxide	H₂O₂, Na₂O₂	-1	Strong oxidizers, bleaching agent
🟢 Superoxide	KO₂, CsO₂	-½	Oxygen source, air purification
🟡 Suboxide	Cu₂O, Cs₁₁O₃	<0 (metal-rich)	Pigments, fungicide, reducing agents

🔹 3. Key Properties

Physical:

🟠 Normal oxides → solids or gases

🟣 Peroxides → colorless liquids or solids, unstable

🟢 Superoxides → colored solids (KO₂ yellow-orange)

🟡 Suboxides → metal-rich solids, often colored

Chemical:

💥 Normal oxides → acidic, basic, or amphoteric

🌬 Peroxides → oxidizing/reducing, decompose to O₂

⚡ Superoxides → react with H₂O & CO₂, release O₂

🔹 Suboxides → reducing agents, can form normal oxides

🔹 4. Uses

🟠 Normal oxides → ceramics, metallurgy

🟣 Peroxides → disinfectants, bleaching, rocket propellant

🟢 Superoxides → air purification, oxygen source

🟡Suboxides→pigments(Cu₂O red),fungicides, semiconductors

🔹 5. Quick Tips

⚡ O–O bond = weak → peroxides & superoxides are reactive

💛 Metal-rich oxides = suboxides, form under limited oxygen

🟠 Amphoteric oxides = react with both acids and bases (e.g., Al₂O₃)

🌬 KO₂ = yellow-orange solid, releases O₂ slowly

🟠🧪 Oxides & Its Types – Interactive Quiz # 1 by Inam Jazbi

1. Which of the following is a normal oxide?
🟥 A) H₂O₂
🟦 B) CO
🟩 C) KO₂
🟨 D) Cs₁₁O₃

2. The oxidation state of oxygen in peroxides is:
🟥 A) -1
🟦 B) -2
🟩 C) -½
🟨 D) 0

3. KO₂ is classified as:
🟥 A) Normal oxide
🟦 B) Peroxide
🟩 C) Superoxide
🟨 D) Suboxide

4. Which oxide is red in color?
🟥 A) Cu₂O
🟦 B) CuO
🟩 C) KO₂
🟨 D) H₂O₂

5. Hydrogen peroxide acts as:
🟥 A) Oxidizing agent only
🟦 B) Reducing agent only
🟩 C) Both oxidizing and reducing agent
🟨 D) Neither

6. Which oxide is metal-rich?
🟥 A) CuO
🟦 B) Suboxide
🟩 C) KO₂
🟨 D) H₂O₂

7. General formula of superoxides is:
🟥 A) MO
🟦 B) MO₂
🟩 C) M₂O₂
🟨 D) ROOR

8. Which oxide is used in air purification in submarines?
🟥 A) KO₂
🟦 B) Cu₂O
🟩 C) H₂O
🟨 D) CO

9. Which of the following is a peroxide?
🟥 A) Na₂O₂
🟦 B) CO
🟩 C) Cu₂O
🟨 D) KO₂

10. Oxides formed by partial oxidation of metals are called:
🟥 A) Peroxides
🟦 B) Superoxides
🟩 C) Suboxides
🟨 D) Normal oxides

11. Which oxide is a powerful oxidizing agent?
🟥 A) H₂O
🟦 B) KO₂
🟩 C) Cu₂O
🟨 D) CO

12. Cs₁₁O₃ belongs to which type?
🟥 A) Normal oxide
🟦 B) Peroxide
🟩 C) Superoxide
🟨 D) Suboxide

13. Oxides with formula ROOR belong to:
🟥 A) Peroxides
🟦 B) Superoxides
🟩 C) Suboxides
🟨 D) Normal oxides

14. Which oxide is used as a fungicide and pigment?
🟥 A) Cu₂O
🟦 B) KO₂
🟩 C) H₂O₂
🟨 D) CsO₂

15. Oxidation state of oxygen in normal oxides is:
🟥 A) -1
🟦 B) -2
🟩 C) -½
🟨 D) 0

16. Peroxides release which gas on decomposition?
🟥 A) CO₂
🟦 B) O₂
🟩 C) H₂
🟨 D) N₂

17. Which oxide has formula CuO?
🟥 A) Copper(I) oxide
🟦 B) Copper(II) oxide
🟩 C) Superoxide
🟨 D) Peroxide

18. Which type of oxide has more metal atoms than oxygen?
🟥 A) Normal oxide
🟦 B) Suboxide
🟩 C) Peroxide
🟨 D) Superoxide

19. Which oxide is yellow-orange in color?
🟥 A) KO₂
🟦 B) Cu₂O
🟩 C) H₂O₂
🟨 D) Cs₁₁O₃

20. Which of the following is both an oxidizing and reducing agent?
🟥 A) KO₂
🟦 B) Cu₂O
🟩 C) H₂O₂
🟨 D) CO

✅ Answers

🟦 B – CO
🟥 A – -1
🟩 C – Superoxide
🟥 A – Cu₂O
🟩 C – Both oxidizing and reducing agent
🟦 B – Suboxide
🟦 B – MO₂
🟥 A – KO₂
🟥 A – Na₂O₂
🟩 C – Suboxides
🟦 B – KO₂
🟨 D – Suboxide
🟥 A – Peroxides
🟥 A – Cu₂O
🟦 B – -2
🟦 B – O₂
🟦 B – Copper(II) oxide
🟦 B – Suboxide
🟥 A – KO₂
🟩 C – H₂O₂

🌟🧪 Oxides & Its Types – Interactive Quiz # 2 by Inam Jazbi

1. Which of the following is an example of a basic oxide?
🟥 A) CO₂
🟦 B) Na₂O
🟩 C) SO₃
🟨 D) P₂O₅
💡 Hint: Basic oxides react with acids to form salts.

2. Which oxide is acidic in nature?
🟥 A) MgO
🟦 B) Al₂O₃
🟩 C) SO₂
🟨 D) CaO
💡 Hint: Acidic oxides usually come from non-metals.

3. H₂O₂ is classified as:
🟥 A) Normal oxide
🟦 B) Peroxide
🟩 C) Superoxide
🟨 D) Suboxide
💡 Hint: Contains O–O single bond.

4. The oxygen oxidation state in superoxides is:
🟥 A) -2
🟦 B) -1
🟩 C) -½
🟨 D) 0
💡 Hint: Superoxides are stronger oxidizers than peroxides.

5. Cu₂O is known as:
🟥 A) Copper(II) oxide
🟦 B) Copper(I) oxide
🟩 C) Suboxide
🟨 D) Peroxide
💡 Hint: Red colored solid.

6. Which oxide reacts with CO₂ to release oxygen?
🟥 A) Cu₂O
🟦 B) KO₂
🟩 C) H₂O
🟨 D) Na₂O
💡 Hint: Used in submarines for air purification.

7. Which oxide is an oxidizing agent and used in bleaching?
🟥 A) CuO
🟦 B) H₂O₂
🟩 C) Na₂O
🟨 D) Cs₁₁O₃
💡 Hint: Also acts as a reducing agent in some reactions.

8. Suboxides are formed when metals are oxidized:
🟥 A) Fully
🟦 B) Partially
🟩 C) Excessively
🟨 D) Never
💡 Hint: Metal-rich oxides with less oxygen.

9. Which oxide has formula KO₂?
🟥 A) Peroxide
🟦 B) Superoxide
🟩 C) Suboxide
🟨 D) Normal oxide
💡 Hint: Yellow-orange solid.

10. Which oxide is commonly used as a red pigment?
🟥 A) Cu₂O
🟦 B) H₂O₂
🟩 C) KO₂
🟨 D) CO₂
💡 Hint: Also used in fungicides.

11. Which oxide is amphoteric in nature?
🟥 A) Al₂O₃
🟦 B) Na₂O
🟩 C) SO₃
🟨 D) CuO
💡 Hint: Can react with both acids and bases.

12. Oxygen oxidation state in peroxides is:
🟥 A) -½
🟦 B) -1
🟩 C) -2
🟨 D) 0
💡 Hint: O–O bond present.

13. Which oxide is used in rocket propellants?
🟥 A) H₂O₂
🟦 B) Cu₂O
🟩 C) CO
🟨 D) KO₂
💡 Hint: Must be highly concentrated.

14. Which oxide reacts with water to form H₂O₂?
🟥 A) KO₂
🟦 B) Na₂O₂
🟩 C) Cu₂O
🟨 D) CO₂
💡 Hint: Also releases O₂ gas.

15. Which type of oxide contains more metal atoms than oxygen?
🟥 A) Normal oxide
🟦 B) Peroxide
🟩 C) Suboxide
🟨 D) Superoxide
💡 Hint: Formed under limited oxygen.