Coordination Compounds is the most scoring chapter in Inorganic Chemistry. Unlike p-Block, it runs on rules, not memory: learn a method for naming, isomerism and magnetic behaviour, and the questions solve themselves. This coordination compounds NEET PYQ analysis shows which question types NTA repeats and the shortcuts that work.
For concept building, pair this with our coordination compounds strategy guide, and see how the chapter fits into our Inorganic Chemistry preparation plan. This article focuses on what past papers actually ask.
Want to test yourself first? Solve the Coordination Compounds PYQs for free, then use this guide to fix the gaps.
Table of Contents
Why This Chapter Is a Must-Do
NEET usually asks two to three questions from Coordination Compounds, which makes it one of the heaviest chapters in Class 12 Inorganic Chemistry.
The chapter leans on hybridisation, so revise our Chemical Bonding PYQ patterns article if shapes feel unclear. It also uses the electronic configurations of transition metals, which the d and f Block notes cover. The Coordination Compounds class notes are handy for the full theory.
Coordination Compounds NEET PYQ Analysis: The Repeated Question Types
When you sort a decade of NEET chemistry PYQs from this chapter, five question types cover almost everything.
| Question type | Frequency | What it tests |
|---|---|---|
| Hybridisation and magnetic behaviour | Most frequent | VBT, unpaired electrons, magnetic moment |
| Isomerism | Very frequent | Type of isomerism, number of isomers |
| Crystal field theory | Very frequent | Splitting, spectrochemical series, colour |
| IUPAC nomenclature | Regular | Naming a complex or writing its formula |
| Ligands, Werner’s theory and uses | Regular | Denticity, ionisable ions, applications |
For a quick warm-up before the full set, try these five quick coordination practice questions.
Ligands and Werner’s Theory
- Primary valency is ionisable and equals the oxidation state. Secondary valency is non-ionisable and equals the coordination number.
- Only ions outside the square bracket are precipitated. So [Co(NH₃)₅Cl]Cl₂ gives 3 ions in solution and 2 moles of AgCl with excess AgNO₃.
- Denticity: Cl⁻, NH₃, H₂O and CN⁻ are monodentate; ethane-1,2-diamine (en) and oxalate are bidentate; EDTA⁴⁻ is hexadentate.
- Ambidentate ligands can bind through two different atoms: NO₂⁻ (N or O) and SCN⁻ (S or N).
- Chelate complexes are more stable than similar complexes with monodentate ligands.
IUPAC Nomenclature in Four Rules
- Name the cation first, then the anion.
- Within the complex, name ligands in alphabetical order, then the metal.
- Anionic ligands end in -o (chlorido, cyanido); neutral ligands keep special names (aqua, ammine, carbonyl).
- If the complex ion is an anion, the metal ends in -ate (ferrate, cuprate, argentate). Give the oxidation state in Roman numerals.
| Formula | Name |
|---|---|
| K₄[Fe(CN)₆] | Potassium hexacyanidoferrate(II) |
| [Co(NH₃)₅Cl]Cl₂ | Pentaamminechloridocobalt(III) chloride |
| [Pt(NH₃)₂Cl₂] | Diamminedichloridoplatinum(II) |
| [Ni(CO)₄] | Tetracarbonylnickel(0) |
Most IUPAC nomenclature errors come from the oxidation state, so calculate it before you read the options.
Isomerism in Coordination Compounds
Structural isomerism
| Type | Example |
|---|---|
| Ionisation | [Co(NH₃)₅SO₄]Br and [Co(NH₃)₅Br]SO₄ |
| Linkage | [Co(NH₃)₅(NO₂)]²⁺ and [Co(NH₃)₅(ONO)]²⁺ |
| Coordination | [Co(NH₃)₆][Cr(CN)₆] and [Cr(NH₃)₆][Co(CN)₆] |
| Solvate (hydrate) | [Cr(H₂O)₆]Cl₃ and [Cr(H₂O)₅Cl]Cl₂·H₂O |
Stereoisomerism
- Geometrical: shown by square planar MA₂B₂ (cis and trans) and octahedral MA₄B₂ (cis and trans) and MA₃B₃ (fac and mer). Tetrahedral complexes do not show it.
- Optical: shown by [Co(en)₃]³⁺ and by the cis form of [Co(en)₂Cl₂]⁺. The trans form is optically inactive.
Hybridisation and Magnetic Behaviour
| Complex | Hybridisation | Shape | Unpaired electrons |
|---|---|---|---|
| [Fe(CN)₆]⁴⁻ | d²sp³ | Octahedral | 0 |
| [Fe(CN)₆]³⁻ | d²sp³ | Octahedral | 1 |
| [FeF₆]³⁻ | sp³d² | Octahedral | 5 |
| [Co(NH₃)₆]³⁺ | d²sp³ | Octahedral | 0 |
| [CoF₆]³⁻ | sp³d² | Octahedral | 4 |
| [Ni(CN)₄]²⁻ | dsp² | Square planar | 0 |
| [NiCl₄]²⁻ | sp³ | Tetrahedral | 2 |
| [Ni(CO)₄] | sp³ | Tetrahedral | 0 |
Strong field ligands (CN⁻, CO, NH₃ with Co³⁺) force pairing and give inner orbital complexes. Weak field ligands (F⁻, Cl⁻, H₂O) give outer orbital complexes.
Spin-only magnetic moment = √[n(n + 2)] BM, where n is the number of unpaired electrons. For n = 1, 2, 3, 4, 5 the values are 1.73, 2.83, 3.87, 4.90 and 5.92 BM.
Crystal Field Theory
- In an octahedral field, the d-orbitals split into lower t₂g (three orbitals) and higher e_g (two orbitals).
- In a tetrahedral field, the order is reversed, and Δt = (4/9)Δo. Tetrahedral complexes are therefore almost always high spin.
- If Δo is greater than the pairing energy, electrons pair up (low spin). If it is smaller, the complex is high spin.
- Spectrochemical series: I⁻ < Br⁻ < Cl⁻ < F⁻ < OH⁻ < C₂O₄²⁻ < H₂O < NH₃ < en < CN⁻ < CO.
- Colour arises from d–d transitions. Complexes with d⁰ or d¹⁰ configuration are colourless.
Crystal field theory questions usually ask you to arrange complexes by Δo or by the wavelength absorbed. A stronger ligand means a larger Δo and a shorter wavelength absorbed.
Uses to remember: cis-platin in cancer treatment, EDTA in lead poisoning, and the metals in chlorophyll (Mg), haemoglobin (Fe) and vitamin B₁₂ (Co).
Worked PYQ-Pattern Questions
Q1. What is the IUPAC name of [Co(NH₃)₄Cl₂]Cl?
Answer: Tetraamminedichloridocobalt(III) chloride. Cobalt is +3: x + 0 − 2 = +1.
Q2. How many unpaired electrons are present in [Fe(CN)₆]³⁻, and what is its magnetic moment?
Answer: 1 unpaired electron; 1.73 BM. Fe³⁺ is d⁵, and CN⁻ forces pairing.
Q3. Which complex shows optical isomerism? (a) [Co(NH₃)₆]³⁺ (b) [Co(en)₃]³⁺ (c) trans-[Co(en)₂Cl₂]⁺ (d) [Ni(CO)₄]
Answer: (b) [Co(en)₃]³⁺.
Q4. How many moles of AgCl are precipitated when excess AgNO₃ is added to one mole of [Cr(H₂O)₅Cl]Cl₂?
Answer: 2 moles. Only the two chloride ions outside the bracket are ionisable.
Q5. What is the hybridisation and shape of [Ni(CN)₄]²⁻?
Answer: dsp², square planar. Ni²⁺ is d⁸, and CN⁻ pairs the electrons to free one d-orbital.
Common Traps in This Chapter
- Counting chloride inside the bracket as ionisable
- Calling [NiCl₄]²⁻ square planar or [Ni(CN)₄]²⁻ tetrahedral
- Looking for geometrical isomers in tetrahedral complexes
- Forgetting the -ate ending for anionic complexes
- Treating H₂O as a strong field ligand
Practise Every Coordination Compounds PYQ
This coordination compounds NEET PYQ analysis gives you the rules and tables. Practice makes them automatic. Every previous year question from this chapter is available chapter-wise, free:
👉 Solve all Coordination Compounds NEET PYQs
For every complex, write three things before you look at the options: the oxidation state, the d-electron count and whether the ligand is strong or weak.
Conclusion
This chapter is rule-based from start to finish. Use this coordination compounds NEET PYQ analysis to master naming, isomer types, the hybridisation table and the spectrochemical series. Then practise until those three steps become a habit.
❓ FAQ
Q: How many questions come from Coordination Compounds in NEET? A: Usually two to three questions, which makes it one of the highest-weightage chapters in Inorganic Chemistry.
Q: What is the most important topic in this chapter? A: Hybridisation with magnetic behaviour is tested most, followed by isomerism, crystal field splitting and naming.
Q: Is this chapter difficult? A: No. It is rule-based, so once you know how to find the oxidation state, d-electron count and ligand strength, most questions are direct.
Q: How do I know if a ligand is strong or weak? A: Use the spectrochemical series. CO, CN⁻ and en are strong field ligands; halides and H₂O are weak field ligands.
Q: How should I revise this chapter for NEET? A: Use a coordination compounds NEET PYQ analysis to list the repeated complexes and rules, learn the hybridisation table, and solve past questions chapter-wise.
Q: Where can I practise these PYQs for free? A: You can solve every previous year question from this chapter for free using the practice link in this article.