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CBSE Class 12 · Chemistry

Coordination Compounds

Official NCERT chapter from Chemistry Part I–II (book code lech1). ExamMaster notes are original teaching at CBSE Class 12 depth.

This lesson follows the official chapter “Coordination Compounds” in Chemistry Part I–II. The words below are ExamMaster’s teaching, not a paste from the book. Use the NCERT chapter for the classroom sequence; use these notes to hold the idea without copying exercises or figures.

  • CBSE Class 12
  • Medium level
  • 8 concepts

1Werner's Theory of Coordination Compounds

Werner: a coordination compound has a metal centre with a fixed number of ligands as taught — primary and secondary valence in the old language if named. Werner is a count-and-link story, not a salt-dump. [Co(NH3)6]Cl3 as the school case if listed.

Treating every double salt as a coordination compound is a miss if the lesson split them.

Figure. Werner's series: as NH3 is replaced by Cl inside the sphere, ionisable Cl⁻ seen by AgNO3 falls 3, 2, 1, 0. Primary valence stays +3; secondary valence (coordination number) stays 6. Bar length is the outer-ion count.

How it works

  1. Name a metal centre and a ligand-countWerner’s look.
  2. Keep a school complex as the caseThe example.
  3. Refuse a simple NaCl as this headingA complex.

2Definitions of Some Important Terms Pertaining to

Terms: ligand, coordination number, coordination sphere as taught — and the leftover heading words the outline kept. A term is a name-plus-test. A ligand donates a pair as framed; CN is how many sit on the metal.

Calling the outer Cl in [Co(NH3)6]Cl3 a ligand of Co is a miss if they sit outside the sphere.

Figure. Terms on one ion: Co is the central metal, six NH3 are the ligands, the coordination number is 6 (donor count in the sphere), and 3+ is the charge of the coordination entity. No octahedron is drawn.

How it works

  1. Name ligand, CN, or the sphereThe term.
  2. Give the school sentenceThe test.
  3. Keep outer ions off the CN if taughtHonest.

3Nomenclature of Coordination Compounds

Nomenclature: the taught IUPAC order — ligands then metal, with oxidation number. [Co(NH3)6]Cl3 as hexaamminecobalt(III) chloride if framed. A name is a rule-output, not a brand.

Numbering ligands as if they were organic locants is a miss.

Figure. IUPAC name order for the cationic complex: ligands in alphabetical stem order (here one kind: hexaammine), then the metal, then the oxidation state in Roman numerals. The formula is [Co(NH3)6]3+.

How it works

  1. List ligands then the metal as taughtThe order.
  2. Add the OS in parenthesesThe name.
  3. Keep it systematicNot a brand.

4Isomerism in Coordination Compounds

Isomerism: geometrical (cis/trans) and optical if taught; linkage or ionisation if named. Same formula, different map. Isomer is a same-count-different-arrange, not a different metal.

Two different metals as “isomers” is a miss.

Figure. Ionization isomers: the same atoms, different ionizable ion. Left, Br is in the sphere and SO4 is outside; right, SO4 is in the sphere and Br is outside. AgNO3 sees different anions. Stereo octahedra are not drawn.

How it works

  1. Check the formula is the sameThe gate.
  2. Name cis/trans or the taught extra typeThe isomer.
  3. Keep the metal the sameHonest.

5Bonding in Coordination Compounds

Bonding: VBT and CFT as taught — hybrid look versus d-split. Bonding is a why-the-shape/colour, not a second name. One octahedral split or an sp3d2 mention is enough.

A covalent-only slogan as the whole bonding is a skip if CFT was taught.

Figure. Octahedral crystal-field ladder. The dashed barycentre sits at the weighted mean: eg is 0.30 above it and t2g is 0.20 below (3:2 = 0.6:0.4 of Δo). The bracket from t2g to eg is Δo. Orbital shapes are not drawn.

How it works

  1. Name VBT hybrids or CFT split as taughtThe picture.
  2. Keep one octahedral caseThe example.
  3. Refuse a university dumpThis class.

6Bonding in Metal Carbonyls

Metal carbonyls: CO as a ligand as taught; a synergic bond if named. Ni(CO)4 as the school case if listed. Carbonyl is a CO-complex, not a carboxylate.

A carboxylic acid labelled carbonyl-complex is a miss.

Figure. Metal-carbonyl bonding is a synergic pair: CO σ-donates into the metal, and the metal π-backs into CO π*. The two arrows are opposite. Carbon, not oxygen, binds the metal. No orbital lobes are drawn.

How it works

  1. Name CO on a metalThe carbonyl.
  2. Keep the taught extra (synergic) if askedHonest.
  3. Refuse an organic acid as this headingA complex.

7Importance and Applications of Coordination

Importance and applications: haemoglobin, catalysis, analysis as taught — one honest use. Application is a use-column, not a brand-ad.

A slogan “complexes do everything” is a mute use.

Figure. Coordination compounds in use: Fe in haemoglobin, Mg in chlorophyll, EDTA wrapping Ca2+ or Pb2+, and cisplatin as a Pt drug. Each edge names the metal, not a structure.

How it works

  1. Name one taught useThe application.
  2. Keep it a school sentenceHonest.
  3. Refuse a brand-adA use.

8A definition is a test you can run

Coordination-word is a test: a centre-plus-ligands, a CN, a name, or an isomer. If you only say “complex”, you have a heading.

A glow-sticker is not the test.

Figure. Werner's definition is a test: add AgNO3 and count the white AgCl. That count is the ionisable Cl⁻ outside the sphere, not the chlorine written in the formula. A picture of an octahedron is not the test.

How it works

  1. Name ligand, CN, name, or isomerThe object.
  2. Give the school sentenceThe test.
  3. Then the word has contentThe definition ran.
A ligand here is
  1. A bit that sits on the metal as taught
  2. The outer counter-ion always
  3. A solvent brand

On the centre.

Notes

  • Mapped to the official NCERT chapter “Coordination Compounds”. Original teaching only — no textbook sentences.
  • Science here is Physics, Chemistry and Biology ideas at this class, never a language or social-science chapter.

Formulas

  • CN = ligand links on the metal as taught
  • name: ligands then metal(OS)

Recap

Hold these pegs from the official chapter “Coordination Compounds”. The wording is ExamMaster’s teaching, not a textbook recap.

Werner's Theory of Coordination Compounds
Werner: a coordination compound has a metal centre with a fixed number of ligands as taught — primary and secondary valence in the old language if named.
Definitions of Some Important Terms Pertaining to
Terms: ligand, coordination number, coordination sphere as taught — and the leftover heading words the outline kept.
Nomenclature of Coordination Compounds
Nomenclature: the taught IUPAC order — ligands then metal, with oxidation number.
Isomerism in Coordination Compounds
Isomerism: geometrical (cis/trans) and optical if taught; linkage or ionisation if named.
Bonding in Coordination Compounds
Bonding: VBT and CFT as taught — hybrid look versus d-split.
Bonding in Metal Carbonyls
Metal carbonyls: CO as a ligand as taught; a synergic bond if named.

Practise Coordination Compounds

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