Coordination Compounds

part 1

Basics of Coordination Compounds

• Werner's theory of coordination compounds
• Ligands — types and definitions
• Central metal atom/ion and coordination number
• IUPAC nomenclature of coordination compounds

part 2

Isomerism and Bonding

• Structural isomerism in coordination compounds
• Stereoisomerism — geometrical and optical
• Valence bond theory of coordination compounds
• Crystal field theory — splitting of d orbitals

part 3

Stability and Applications

• Crystal field splitting — strong and weak field ligands
• Colour in coordination compounds
• Stability of coordination compounds
• Applications — analytical chemistry, medicine, industry

Octahedral geometry — hybridisation

$sp^3d^2$ or $d^2sp^3$

★ board favourite

Tetrahedral geometry — hybridisation

$sp^3$

★ board favourite

Square planar geometry — hybridisation

$dsp^2$

★ board favourite

Werner's theory: primary & secondary valency

Primary = oxidation state; Secondary = coordination number

★ frequently asked

VBT: inner orbital complexes (low spin)

Use inner (n−1)d orbitals; diamagnetic/low spin

★ frequently asked

VBT: outer orbital complexes (high spin)

Use outer nd orbitals; paramagnetic/high spin

★ frequently asked

Geometrical isomerism: cis and trans

cis-[Pt(NH₃)₂Cl₂]: both Cl same side

★ frequently asked

Optical isomerism: d and l enantiomers

Non-superimposable mirror images; rotate plane-polarised light

★ frequently asked

Using valence bond theory, predict the hybridisation, geometry and magnetic behaviour of [Ni(CN)₄]²⁻ and [NiCl₄]²⁻. (Atomic number of Ni = 28)

Write the IUPAC names of: (i) [Cr(NH₃)₃(H₂O)₃]Cl₃ and (ii) K₃[Fe(C₂O₄)₃].

Give the IUPAC name of [Fe(CN)₆]³⁻. What type of isomerism is shown by [Co(NH₃)₄Cl₂]⁺? Draw both isomers.

(a) What is meant by linkage isomerism, ionisation isomerism and coordination isomerism? Give one example of each. (b) Draw the geometrical isomers of [Co(en)₂Cl₂]⁺.

Explain Crystal Field Theory (CFT) for octahedral complexes. Why do [Co(NH₃)₆]³⁺ and [CoF₆]³⁻ have different colours? Predict the magnetic behaviour of each.

On the basis of crystal field theory, explain why [Ti(H₂O)₆]³⁺ is coloured while [Sc(H₂O)₆]³⁺ is colourless. Define the crystal field splitting energy Δ₀.

What is the coordination number of the central metal ion in [Co(en)₃]³⁺?

Explain the following terms with one example each: (i) ambidentate ligand, (ii) chelate, (iii) denticity of a ligand.

What is meant by the stability constant of a coordination complex? Why is [Fe(CN)₆]³⁻ more stable than [Fe(H₂O)₆]³⁺?

Out of NH₃ and H₂O, which is a stronger field ligand according to the spectrochemical series?

How many marks is Coordination Compounds worth in the Class 12 board exam?

Around 7 marks of the 70-mark CBSE Chemistry theory paper, based on the official unit-wise weightage. IUPAC names, isomerism types, CFT — tough but high marks.

Is Coordination Compounds easy or hard?

It's rated hard — one of the tougher chapters in Class 12 Chemistry. Most students need about 5 hours to cover it well.

What are the important topics in Coordination Compounds?

The chapter covers 11 NCERT topics in 3 areas: Basics of Coordination Compounds; Isomerism and Bonding; Stability and Applications.

What questions come from Coordination Compounds in board exams?

Between 2018–2024, CBSE board papers asked questions from this chapter on Valence Bond Theory, IUPAC Nomenclature, Isomerism, Crystal Field Theory — 1- to 5-mark questions.