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Coordination Compounds

NCERT Class 12 Chemistry Chapter 5

Coordination Compounds for Class 12 Chemistry, JEE and NEET: Werner’s theory, ligands, IUPAC names, isomerism, valence bond and crystal field theories.

8 topics Updated 8 Nov 2026

For: Class 12, JEE and NEET, unless a topic says otherwise

In the syllabus: JEE Class 12 syllabus, NEET Class 12 syllabus

With your textbook

NCERT Chemistry Part I (Class 12), Chapter 5 “Coordination Compounds”, reprint 2026-27.

Open the official NCERT chapter (PDF, 3.7 MB, ncert.nic.in)

Checked on 19 Oct 2026.

Learn in this order

  1. Werner’s theory of coordination compounds

    Postulates, primary and secondary valency, the AgCl test, and double salts vs complexes, with solved examples.

    NCERT Section 5.1 12 min read 3 solved examples 6 practice questions

  2. Experiment: preparation of Mohr’s salt and potash alum

    Double salts from equimolar mixtures, why dilute HSO is added, procedure and precautions.

    JEE and NEET only 10 min read 2 solved examples 5 practice questions

  3. Ligands, coordination number and other terms

    Denticity, chelates, ambidentate ligands, coordination number, sphere and polyhedron, oxidation number, with examples.

    NCERT Section 5.2 13 min read 3 solved examples 7 practice questions

  4. Nomenclature of coordination compounds

    Rules for formulas and names, ligand names, -ate anions, with worked examples.

    NCERT Section 5.3 12 min read 5 solved examples 8 practice questions

  5. Isomerism in coordination compounds

    Geometrical (cis, trans, fac, mer), optical, linkage, coordination, ionisation and solvate.

    NCERT Section 5.4 14 min read 4 solved examples 7 practice questions

  6. Bonding in coordination compounds: VBT and CFT

    Inner and outer orbital complexes, magnetism, high and low spin, spectrochemical series, colour.

    NCERT Section 5.5 20 min read 4 solved examples 9 practice questions

  7. Bonding in metal carbonyls

    Homoleptic carbonyls and their shapes, σ donation, back bonding and synergic bonding in the M–CO bond.

    NCERT Section 5.6 9 min read 2 solved examples 4 practice questions

  8. Importance and applications of coordination compounds

    Qualitative analysis, EDTA and hardness, gold and nickel, haemoglobin, cis-platin.

    NCERT Section 5.7 11 min read 3 solved examples 4 practice questions

Key formulas in this chapter

Werner’s theory

  • [Co(NH)]Cl: 1: 3 electrolyte, 3 mol AgCl
  • [CoCl(NH)]Cl: 1: 2 electrolyte, 2 mol AgCl
  • [CoCl(NH)]Cl: 1: 1 electrolyte, 1 mol AgCl
  • Secondary valence = coordination number

Experiment: double salts

  • FeSO + (NH)SO + 6HO → FeSO·(NH)SO·6HO
  • KSO + Al(SO) + 24HO → KSO·Al(SO)·24HO
  • Percentage yield = actual mass ÷ theoretical mass × 100

Ligands and other terms

  • Coordination number = number of donor atoms bonded to the metal
  • Oxidation number + sum of ligand charges = charge on the entity
  • Denticity: NH 1, en 2, CO 2, EDTA 6

Nomenclature

  • Formula: metal first, then ligand formulas or abbreviations in alphabetical order, all in square brackets; an ion’s charge as a right superscript
  • Name: cation, then anion; ligands (alphabetical) + metal (-ate in an anion) + (oxidation state)
  • Oxidation state = charge on the entity − sum of ligand charges

Isomerism

  • Square planar [MXL]: cis and trans
  • Octahedral [MXL]: cis and trans; [Mab]: fac and mer
  • Octahedral [M(L–L)]: d and l; [MX(L–L)]: trans + cis (d and l) = 3 stereoisomers

Bonding: VBT and CFT

  • Octahedral: eg = +0.6Δo, t2g = −0.4Δo
  • Tetrahedral: Δt = (4/9)Δo
  • Spin-only moment: μ = √[n(n + 2)] BM
  • d in an octahedral field: t2g eg if Δo < P; t2g eg if Δo > P

Metal carbonyls

  • σ bond: C lone pair → vacant metal orbital
  • π bond: filled metal d orbital → vacant antibonding π orbital of CO
  • Metal oxidation state in neutral homoleptic carbonyls: 0

Importance and applications

  • Hypo fixing: AgBr + 2NaSO → Na[Ag(SO)] + NaBr
  • Nickel purification: Ni + 4CO → [Ni(CO)] → Ni + 4CO
  • EDTA titration: moles of EDTA = moles of (Ca + Mg)

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