Coordination Compounds for NEET UG
Coordination compounds have a central metal ion surrounded by ligands. They give haemoglobin, chlorophyll and vitamin B₁₂ their roles, and their colours and magnetism follow from crystal field theory.
ChemistryClass 1268 MCQs2 lessons13 flashcards4 memory tricks
Practise Coordination Compounds free
What you'll learn
- Ligands, coordination number and naming
Identify ligands, find the coordination number and oxidation state, and name complexes. - Isomerism and crystal field theory
Identify isomers of complexes and use crystal field splitting to explain colour and magnetism.
Key formulas
| Spectrochemical series (weak → strong field) | I⁻ < Br⁻ < Cl⁻ < F⁻ < OH⁻ < H₂O < NH₃ < en < CN⁻ < CO |
|---|
Memory tricks
In [Co(NH₃)₆]Cl₃, primary valency = 3 (the oxidation state, the ionisable Cl⁻). Secondary valency = 6 (the coordination number, non-ionisable).
I⁻ < Br⁻ < Cl⁻ < F⁻ < OH⁻ < H₂O < NH₃ < en < CN⁻ < CO. Strong-field ligands at the end cause pairing (low-spin complexes).
Bidentate and polydentate ligands form rings with the metal and give more stable complexes than similar monodentate ligands.
K₄[Fe(CN)₆] is potassium hexacyanidoferrate(II). Others: cuprate, argentate, aurate, plumbate, stannate.
Try 3 NEET-style questions
Q1. A complex in which the metal is bound to more than one kind of donor group, such as [Co(NH₃)₄Cl₂]⁺, is called
- homoleptic
- a double salt
- heteroleptic
- a chelate only
Show answer
Answer: (3) heteroleptic
Complexes with only one kind of ligand are homoleptic (e.g. [Co(NH₃)₆]³⁺). Those with more than one kind, like [Co(NH₃)₄Cl₂]⁺, are heteroleptic.
Q2. The shapes of Fe(CO)₅ and Cr(CO)₆ are, respectively,
- octahedral and tetrahedral
- tetrahedral and square planar
- square pyramidal and linear
- trigonal bipyramidal and octahedral
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Answer: (4) trigonal bipyramidal and octahedral
Fe(CO)₅ is trigonal bipyramidal; Cr(CO)₆ is octahedral; Ni(CO)₄ is tetrahedral.
Q3. Which of the following is an ambidentate ligand?
- NH₃
- H₂O
- NO₂⁻
- ethane-1,2-diamine
Show answer
Answer: (3) NO₂⁻
NO₂⁻ can bind to a metal through nitrogen (nitro) or through oxygen (nitrito), so it is ambidentate.
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