Class 12 Chemistry Inorganic Notes 2025 – Full Chapter-wise Explanation, Formulas & Examples

Inorganic Chemistry is one of the most scoring parts of Class 12 Chemistry. It deals with the study of elements, their compounds, coordination complexes, and periodic properties.
Understanding Inorganic Chemistry helps students build a strong base for JEE, NEET, and Board Exams.
Let’s explore each chapter of Inorganic Chemistry in detail with important concepts, reactions, and examples.

Class 12 Chemistry Inorganic Notes 2025 – Full Chapter-wise Explanation, Formulas & Examples

Chapter 1: The Solid State

Overview:

This chapter deals with the structure, packing, and properties of solids.

Types of Solids:

1. Crystalline solids – Have long-range order (e.g., NaCl, diamond)

2. Amorphous solids – Irregular arrangement (e.g., glass, plastic)

Formulas:

• Density of Unit Cell:

  Density (ρ)=Z×Ma3×NA\text{Density (ρ)} = \frac{Z \times M}{a^3 \times N_A}Density (ρ)=a3×NA​Z×M​

  Where,
  $Z$ = number of atoms per unit cell
  $M$ = molar mass
  $a$ = edge length
  NAN_ANA​ = Avogadro’s number

Example:

If NaCl has a face-centered cubic structure, $Z=4$.

Chapter 2: Solutions

Overview:

This chapter explains concentration of solutions, Raoult’s law, colligative properties, and abnormal molecular masses.

Important Formulas:

• Molarity (M) = moles of solute / volume of solution (in L)

• Molality (m) = moles of solute / mass of solvent (in kg)

• Raoult’s Law:
  P1=X1P10P_1 = X_1 P_1^0P1​=X1​P10​

Example:

Calculate vapor pressure lowering if mole fraction of solute is 0.2 → ΔP=X2P10\Delta P = X_2 P_1^0ΔP=X2​P10​

Chapter 3: Electrochemistry

Overview:

Electrochemistry studies electrochemical cells, electrode potential, and conductance.

Key Formula:

Ecell=Ecathode−EanodeE_{cell} = E_{cathode} – E_{anode}Ecell​=Ecathode​−Eanode​ ΔG=−nFEcell\Delta G = -nFE_{cell}ΔG=−nFEcell​

Example:

For Daniell cell:
Zn(s) + Cu²⁺(aq) → Zn²⁺(aq) + Cu(s)
E° = 1.10 V

Chapter 4: Chemical Kinetics

Overview:

It deals with the rate of reaction and factors affecting it.

Rate Law:

Rate=k[A]m[B]n\text{Rate} = k[A]^m [B]^nRate=k[A]m[B]n

Half-life for First Order:

t1/2=0.693kt_{1/2} = \frac{0.693}{k}t1/2​=k0.693​

Example:

If rate constant k=0.693 s−1k = 0.693 \, s^{-1}k=0.693s−1, then t1/2=1st_{1/2} = 1st1/2​=1s

Chapter 5: Surface Chemistry

Overview:

It includes adsorption, catalysis, and colloids.

Types of Adsorption:

• Physical Adsorption – Weak van der Waals forces

• Chemical Adsorption – Strong chemical bonds

Freundlich Adsorption Isotherm:

xm=kP1/n\frac{x}{m} = k P^{1/n}mx​=kP1/n

Example:

Adsorption of gases on charcoal.

Chapter 6: General Principles and Processes of Isolation of Elements

Overview:

This chapter explains metallurgy, i.e., extraction of metals from ores.

Key Steps:

1. Concentration of Ore

2. Roasting and Calcination

3. Reduction

4. Electrolytic Refining

Example:

• Extraction of Aluminum (Hall–Heroult process)

• Extraction of Iron (Blast Furnace)

Chapter 7: The p-Block Elements

Overview:

Focuses on Group 15, 16, 17, and 18 elements.

Group 15 (Nitrogen Family):

• Common oxidation states: +3, +5

• Example: Ammonia (NH₃), Nitric acid (HNO₃)

Important Reaction:

NH3+O2→Pt,800°CNO+H2ONH_3 + O_2 \xrightarrow{Pt, 800°C} NO + H_2ONH3​+O2​Pt,800°C​NO+H2​O

Group 16 (Oxygen Family):

• Ozone formation:

  3O2→UV2O33O_2 \xrightarrow{UV} 2O_33O2​UV​2O3​

Group 17 (Halogens):

• Form salts with metals → NaCl, KBr

Group 18 (Noble Gases):

• Inert gases, but form compounds like XeF₂, XeOF₄

Chapter 8: The d- and f-Block Elements

Overview:

Deals with transition and inner transition metals.

Properties:

• Variable oxidation states

• Colored compounds

• Formation of complexes

Example:

• Mn²⁺ → light pink

• Fe³⁺ → yellow-brown

Important Reaction:

2CrO42−+2H+→Cr2O72−+H2O2CrO_4^{2-} + 2H^+ → Cr_2O_7^{2-} + H_2O2CrO42−​+2H+→Cr2​O72−​+H2​O

Chapter 9: Coordination Compounds

Overview:

Coordination compounds consist of a central metal atom bonded to ligands.

Important Terms:

• Ligand: Molecule attached to central metal (e.g., NH₃, H₂O)

• Coordination Number: Number of ligand atoms directly attached to metal.

Nomenclature Example:

[Co(NH3)6]Cl3→Hexaamminecobalt(III)chloride[Co(NH_3)_6]Cl_3 → Hexaamminecobalt(III) chloride[Co(NH3​)6​]Cl3​→Hexaamminecobalt(III)chloride

Werner’s Theory:

Explains primary and secondary valencies in complexes.

Chapter 10: Haloalkanes and Haloarenes (Overlap between Organic and Inorganic Concepts)

Overview:

Compounds containing halogens (F, Cl, Br, I) attached to alkyl or aryl groups.

Example Reaction:

CH3CH2OH+HCl→ZnCl2CH3CH2Cl+H2OCH_3CH_2OH + HCl \xrightarrow{ZnCl_2} CH_3CH_2Cl + H_2OCH3​CH2​OH+HClZnCl2​​CH3​CH2​Cl+H2​O

Chapter 11: Coordination Compounds (Advanced Examples)

Crystal Field Theory (CFT):

• Splitting of d-orbitals occurs in a ligand field.

• High-spin vs. low-spin complexes

Example:

[Fe(CN)6]4−→low-spin (strong field ligand)[Fe(CN)_6]^{4-} → \text{low-spin (strong field ligand)}[Fe(CN)6​]4−→low-spin (strong field ligand) [FeF6]3−→high-spin (weak field ligand)[FeF_6]^{3-} → \text{high-spin (weak field ligand)}[FeF6​]3−→high-spin (weak field ligand)

Chapter 12: The f-Block Elements

Overview:

Contains Lanthanides and Actinides.

Characteristics:

• Show variable oxidation states

• Exhibit lanthanide contraction

Example:

Ce⁴⁺ → strong oxidizing agent
U³⁺ → reducing agent

Chapter 13: Environmental Chemistry

Overview:

Studies chemical processes in the environment.

Main Topics:

• Air pollution: CO, SO₂, NOx

• Water pollution: Heavy metals

• Green chemistry: Use of eco-friendly methods

Example:

Formation of acid rain:

SO2+O2+H2O→H2SO4SO_2 + O_2 + H_2O → H_2SO_4SO2​+O2​+H2​O→H2​SO4​

Summary Table:

Conclusion

Inorganic Chemistry forms the foundation of chemical science. Mastering the concepts, memorizing key reactions, and understanding trends across the periodic table help students excel in Boards, JEE, and NEET.
Regular practice of formulas and NCERT examples is the key to success in this section.

FAQs on Class 12 Chemistry Inorganic

Q1. How many chapters are there in Class 12 Inorganic Chemistry?

There are about 6–7 major chapters under Inorganic Chemistry in Class 12 syllabus.

Q2. Which Inorganic chapter is most important for Board exams?

The p-block elements and Coordination Compounds are highly important for both board and competitive exams.

Q3. How to remember reactions in Inorganic Chemistry?

Use visual charts, mnemonics, and group-wise study to retain reactions effectively.

Q4. What is lanthanide contraction?

It is the gradual decrease in ionic radii of lanthanides from La³⁺ to Lu³⁺ due to poor shielding of 4f electrons.

Q5. What are ligands?

Ligands are molecules or ions that donate electron pairs to a central metal atom to form coordination compounds.

Q6. Which is the strongest field ligand?

According to the Spectrochemical Series, CN⁻ is one of the strongest field ligands.

Q7. Why transition metals form colored compounds?

Due to d–d electronic transitions within partially filled d-orbitals.

Q8. What is the difference between physical and chemical adsorption?

Physical adsorption involves weak van der Waals forces; chemical adsorption involves strong bond formation.

Q9. Which metal is extracted using the Hall–Heroult process?

Aluminum (Al) is extracted by this electrolytic process.

Q10. What is the oxidation state of iron in Fe₂O₃?

Oxidation state of Fe = +3.

Class 12 Chemistry Inorganic

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