CBSE Class 12 Chemistry 2026 Day 4: Coordination Compounds Important Questions, IUPAC Naming, Isomerism & PYQs

Day 4 Coordination Compounds revision for CBSE Class 12 Chemistry Board Exam 2026: check important questions, MCQs, PYQ trends, IUPAC nomenclature rules, isomerism (structural and stereoisomerism), VBT vs CFT, spectrochemical series, magnetic moment numericals and applications like EDTA and cisplatin. High-scoring inorganic chapter covering naming of complexes, coordination number, bonding theory, magnetism and predictable board exam concepts for last-minute smart revision.

Day 4 : Coordination Compounds – 30+ Important Questions, MCQs, PYQ Analysis & Tips for CBSE Class 12 Chemistry Board Exam 2026

Only 3 days remain for the CBSE Class 12 Chemistry Board Exam scheduled on 28 February 2026. After mastering Physical Chemistry (Solutions, Electrochemistry, Kinetics) and d-block elements, today’s focus is one of the most important scoring chapters in Inorganic Chemistry — Coordination Compounds.

This chapter carries around 7 marks in the board exam and appears almost every year through naming questions, isomerism, bonding theory, and short explanations. The advantage? It is concept-based and predictable. If you revise it correctly, you can secure nearly full marks.

Coordination compounds also connect with real life — medicines (cisplatin cancer drug), chlorophyll, haemoglobin, water treatment using EDTA, and industrial catalysts.

Quick Revision Notes

• 1. Central metal atom/ion: Accepts electron pair
• 2. Ligand: Electron pair donor (Lewis base)
• 3. Coordination Number (CN): Number of donor atoms attached
• 4. Coordination Sphere: Species inside square brackets
• 5. Oxidation state: Charge on metal ion

Examples:

• [Co(NH₃)₆]³⁺ → CN = 6
• [Cu(NH₃)₄]²⁺ → CN = 4
• [Ni(CO)₄] → CN = 4

IUPAC Naming Rules (Most Important)

• 1. Name ligands first (alphabetical order)
• 2. Then name the metal with oxidation state in Roman numerals
• 3. Anionic complex → metal name ends with –ate
• 4. Neutral ligands special names: NH₃ = ammine, H₂O = aqua, CO = carbonyl

Isomerism in Coordination Compounds

1. Structural Isomerism

• Ionisation isomerism
• Hydrate isomerism
• Linkage isomerism
• Coordination isomerism
• 
  

2. Stereoisomerism

• Geometrical (cis-trans)
• Optical isomerism

Important Example: [PtCl₂(NH₃)₂]

• Cis form → anticancer drug (cisplatin)
• Trans form → inactive

Bonding Theories

Valence Bond Theory (VBT)

• 1. Explains hybridisation
• 2. Predicts geometry
• 3. Does NOT explain colour
• 
  

Crystal Field Theory (CFT)

• 1. Explains splitting of d-orbitals
• 2. Explains colour & magnetism
• 3. Octahedral splitting: t₂g (lower) and e_g (higher)
• 
  

Spectrochemical Series (Weak → Strong field):
I⁻ < Br⁻ < Cl⁻ < F⁻ < OH⁻ < H₂O < NH₃ < en < NO₂⁻ < CN⁻ < CO

Important MCQs 

1. 1. Coordination number of Cr in [Cr(en)₃]³⁺ is 6
2. 2. Linkage isomerism shown by [Co(NH₃)₅NO₂]²⁺
3. 3. Strong field ligand: CN⁻
4. 4. [Ni(CO)₄] geometry: Tetrahedral
5. 5. Colorless complex: [Zn(NH₃)₄]²⁺
6. 6. Cis-platin used in: Cancer treatment
7. 7. Hybridisation of square planar complex: dsp²
8. 8. Ambidentate ligand: SCN⁻
9. 9. Magnetic moment formula: √[n(n+2)] BM
10. 10. EDTA is: Hexadentate ligand

Important Questions 

• 1. Define ligand and coordination number
• 2. Explain chelate effect
• 3. Write IUPAC name of given complexes
• 4. Explain geometrical and optical isomerism
• 5. Difference between VBT and CFT
• 6. Draw cis-trans isomers of [Co(NH₃)₄Cl₂]⁺
• 7. Applications of coordination compounds

Magnetism Numerical Example

Calculate magnetic moment of Fe³⁺ (d⁵ high spin):

μ = √[n(n+2)] n = 5 unpaired electrons

μ = √[5(7)] = √35 ≈ 5.92 BM

Common Mistakes Students Make

• 1. Wrong alphabetical order of ligands
• 2. Forgetting oxidation state
• 3. Confusing nitro (NO₂) and nitrito (ONO)
• 4. Not drawing diagrams for isomers
• 5. Ignoring spectrochemical series

PYQ Trend

• 1. IUPAC naming (every year)
• 2. Geometrical isomerism
• 3. Magnetic moment calculation
• 4. VBT vs CFT comparison
• 5. EDTA and cisplatin applications