Class 12 Chemistry Chapter 5: Coordination Compounds Notes for NEET & JEE (PDF + MCQs)

 

Class 12 Chemistry Chapter 5: Coordination Compounds | Complete Notes for NEET & JEE

Introduction

Coordination Compounds are one of the most important chapters in Class 12 Chemistry for both NEET and JEE examinations. This chapter explains how central metal atoms or ions bond with surrounding ligands to form complex structures.

Coordination chemistry is widely used in:

• Biological systems (Hemoglobin, Chlorophyll)

• Industrial catalysts

• Analytical chemistry

• Medicine (Vitamin B12, chelation therapy)

A strong understanding of this chapter helps students solve advanced questions in inorganic chemistry with confidence.

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Why is Coordination Compounds Important?

✔ Very Important for NEET & JEE Inorganic Chemistry
✔ High-weightage chapter in competitive exams
✔ Conceptual + Numerical questions are asked
✔ Important for naming and structure-based problems
✔ Foundation for Bioinorganic Chemistry

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Download Study Material

📘 Complete Coordination Compounds Notes PDF

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What is a Coordination Compound?

A coordination compound is a chemical compound in which a central metal atom or ion is bonded to a fixed number of surrounding ions or molecules called ligands.

Example:

[Co(NH₃)₆]Cl₃

Here:

• Co³⁺ = Central metal ion

• NH₃ = Ligand

• Cl⁻ = Counter ion

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Key Terms in Coordination Chemistry

1. Central Metal Atom/Ion

The positively charged metal ion that forms bonds with ligands.

Examples:

• Fe²⁺

• Co³⁺

• Ni²⁺

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2. Ligands

Ligands are ions or molecules that donate electron pairs to the central metal atom.

Types of Ligands:

• Monodentate: NH₃, Cl⁻, H₂O

• Bidentate: Oxalate (C₂O₄²⁻)

• Polydentate: EDTA

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3. Coordination Number

The number of ligand donor atoms directly bonded to the central metal ion.

Examples:

• [Co(NH₃)₆]³⁺ → Coordination number = 6

• [Ni(CN)₄]²⁻ → Coordination number = 4

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Types of Coordination Compounds

1. Homoleptic Complex

All ligands are identical.

Example:
[Co(NH₃)₆]³⁺

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2. Heteroleptic Complex

Different types of ligands are present.

Example:
[Co(NH₃)₄Cl₂]⁺

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Daily Practice Problems (DPP)

📝 Coordination Compounds DPP Sheet

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Werner’s Theory of Coordination Compounds

Alfred Werner proposed the first theory of coordination compounds.

Postulates:

1. Metal shows two types of valency:

   • Primary valency (ionizable)

   • Secondary valency (coordination number)

2. Secondary valencies are fixed and directional.

3. Ligands satisfy secondary valency.

4. Complex formation occurs through secondary valency.

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IUPAC Nomenclature Rules

Steps:

1. Name ligands first (alphabetical order)

2. Name central metal atom

3. Add oxidation state in Roman numerals

4. Use prefixes:

   • di, tri, tetra, penta, hexa

Example:

[Co(NH₃)₆]Cl₃
→ Hexaammine cobalt (III) chloride

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Isomerism in Coordination Compounds

1. Structural Isomerism

• Ionization isomerism

• Hydrate isomerism

• Linkage isomerism

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2. Stereoisomerism

• Geometrical isomerism (cis-trans)

• Optical isomerism

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Crystal Field Theory (CFT)

CFT explains splitting of d-orbitals in the presence of ligands.

Octahedral Complex:

d-orbitals split into:

• t₂g (lower energy)

• e_g (higher energy)

Importance:

• Explains color of complexes

• Explains magnetic properties

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Applications of Coordination Compounds

✔ Extraction of metals (metallurgy)
✔ Biological systems (Hemoglobin, Chlorophyll)
✔ Analytical chemistry
✔ Catalysis in industries
✔ Medicine (EDTA in lead poisoning)

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Practice Exercises

📘 Coordination Compounds Exercise Sheet

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Important Points for Revision

✔ Coordination compounds contain central metal + ligands
✔ Coordination number = number of donor atoms
✔ Ligands donate electron pairs
✔ Werner’s theory is the foundation
✔ Isomerism plays a key role in structure
✔ CFT explains color and magnetism

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NEET & JEE Quick Revision

✔ Hexaammine complexes have coordination number 6
✔ Ligands are Lewis bases
✔ Metal ion acts as Lewis acid
✔ CFT is important for transition metals
✔ Naming is very important for exams

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Frequently Asked Questions (FAQs)

Q1. What is the most important part of Coordination Compounds?

Nomenclature, isomerism, and Crystal Field Theory are the most important topics.

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Q2. How many questions come from this chapter?

Usually 2–3 questions in NEET and 2–4 questions in JEE.

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Q3. Why is this chapter important?

It is a high-scoring inorganic chemistry chapter with direct and conceptual questions.

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Conclusion

Coordination Compounds is a highly scoring chapter in Class 12 Chemistry. A strong understanding of ligands, coordination number, isomerism, and Crystal Field Theory can help students solve both NEET and JEE questions easily.

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