# Coordination Compounds Notes, Class 12 Chemistry | SwaVid Coordination Compounds, NCERT Class 12 Chemistry: notes with key ideas, formulas, common mistakes and 3 quick checks with worked answers. Canonical: https://www.swavid.com/cbse/class-12/chemistry/chapter/coordination-compounds Source: https://www.swavid.com/cbse/class-12/chemistry/chapter/coordination-compounds # Coordination Compounds ## Formulas and definitions ## Key ideas ## Common mistakes ## Quick checks ## Keep going ## Questions parents ask ## Class 12 Chemistry on SwaVid ### Werner's coordination theory ### Basic coordination entities and terminology ### IUPAC nomenclature rules ### Structural and stereoisomerism ### Valence bond theory ### Crystal field theory ### Bonding in metal carbonyls ### Next chapter ### Related chapter ### Related chapter ### All chapters SwaVid › CBSE › Class 12 › Chemistry › Coordination Compounds Notes written by SwaVid from the NCERT textbook. Class 12 Chemistry, Unit 5. Key ideas, formulas and common mistakes. CBSE prints 7 marks for Unit 5, not for this chapter alone. Short answer. This chapter explains coordination compounds where central metal atoms or ions bind to neutral molecules or anions called ligands. Students learn Werner's theory, systematic IUPAC nomenclature, isomerism, and bonding models including valence bond theory and crystal field theory. Source: NCERT Chemistry Part I (Reprint 2026-27) , Unit 5, Coordination Compounds Metals in coordination compounds show primary and secondary valencies. Primary valencies are ionisable and satisfied by negative ions, whereas secondary valencies are non-ionisable, directional, and equal to the coordination number. A coordination entity consists of a central metal ion surrounded by ligands inside square brackets. Ligands donate lone pairs and are classified by denticity as unidentate, didentate, or polydentate, including ambidentate ligands and chelating ligands. Cations are named before anions, and ligands are named alphabetically before the metal atom. The oxidation state of the metal is written in Roman numerals in parentheses, and the metal name ends in -ate if the complex entity is an anion. Coordination compounds display structural isomerism such as ionisation, solvate, linkage, and coordination isomerism. They also exhibit stereoisomerism as geometrical (cis-trans or facial-meridional) and optical isomers. Under valence bond theory, the central metal provides empty hybrid orbitals to form coordinate bonds with ligand lone pairs. Complexes are classified as inner orbital (d²sp³) or outer orbital (sp³d²) depending on whether inner or outer d orbitals are used. Crystal field theory treats the metal-ligand interaction as purely electrostatic, causing the five degenerate d orbitals to split in an octahedral or tetrahedral field. Strong field ligands cause greater crystal field splitting (Δₒ) and pair up electrons, while weak field ligands form high-spin complexes. Homoleptic metal carbonyls contain both σ and π bonds. A σ bond forms by donation of carbon lone pairs to vacant metal orbitals, while a π bond forms by back-donation of electrons from filled metal d orbitals into empty antibonding π* orbitals of carbon monoxide, creating a synergic effect. Try each question first. Then tap it to see the answer. Fe²⁺ has electronic configuration [Ar] 3d⁶. H₂O is a weak field ligand (Δₒ < P), so the configuration is t2g⁴ eg², giving n = 4 unpaired electrons. μ = √[4 × (4 + 2)] = √24 ≈ 4.90 BM. 4.90 BM Two moles of AgCl precipitated per mole means exactly two chloride ions are ionisable and exist outside the coordination sphere. The remaining one Cl⁻ and five H₂O molecules are inside the sphere: [Cr(H₂O)₅Cl]Cl₂. The total number of coordinated donor atoms is 5 + 1 = 6, so secondary valency is 6. Secondary valency is 6; formula is [Cr(H₂O)₅Cl]Cl₂ Let the oxidation state of Co be x. The ligand charges are en = 0, Cl⁻ = -1, and ONO⁻ = -1. x + 2(0) + (-1) + (-1) = +1, which gives x - 2 = +1, so x = +3. Denticity of two 'en' ligands is 2 × 2 = 4, and each of Cl⁻ and ONO⁻ contributes 1, giving coordination number = 4 + 1 + 1 = 6. Oxidation state is +3; coordination number is 6 Haloalkanes and Haloarenes . The d- and f-Block Elements . Chemical Kinetics . The 10 chapters of Class 12 Chemistry . CBSE does not give marks to one chapter. It prints 7 marks for Unit 5, Coordination Compounds, which includes Coordination Compounds. No. They are written by SwaVid from the NCERT textbook. The CBSE curriculum is the reference for what is assessed. Haloalkanes and Haloarenes. SwaVid is an AI tutor for Indian students in Classes 6 to 12. It finds the earlier ideas a child missed, then teaches today’s chapter. Start free to see how it works. - Unit 5 NCERT book - 7 marks, Unit 5 - 3 quick checks - Naming the central metal without ending in -ate when the complex ion is an anion . Check the net charge of the coordination entity in brackets. If it is negative, modify the metal name to end in -ate, such as ferrate for iron or cobaltate for cobalt. - Equating coordination number to the number of ligand molecules instead of donor atoms . Multiply the number of each ligand by its denticity. For example, [Co(en)₃]³⁺ contains three ethylenediamine ligands, but because each is didentate, the coordination number is 6. - Confusing primary valency with secondary valency in Werner's formulation . Remember that primary valency corresponds to the formal oxidation state of the metal, while secondary valency corresponds to its coordination number. - Writing numerical prefixes like di- or tri- for complex ligands that already contain a Greek prefix . Use bis-, tris-, or tetrakis- followed by the ligand name in parentheses when the ligand name already contains a numerical prefix, as in tris(ethane-1,2-diamine). ## Key Links - [CBSE](https://www.swavid.com/cbse) - [Class 12](https://www.swavid.com/cbse/class-12) - [Chemistry](https://www.swavid.com/cbse/class-12/chemistry/chapters) - [Start free →](https://www.swavid.com/signup) - [All 10 chapters](https://www.swavid.com/cbse/class-12/chemistry/chapters) - [NCERT Chemistry Part I (Reprint 2026-27)](https://ncert.nic.in/textbook.php) - [Open notes](https://www.swavid.com/cbse/class-12/chemistry/chapter/haloalkanes-and-haloarenes) - [Open notes](https://www.swavid.com/cbse/class-12/chemistry/chapter/the-d-and-f-block-elements) - [Open notes](https://www.swavid.com/cbse/class-12/chemistry/chapter/chemical-kinetics) - [Class 12 Chemistry](https://www.swavid.com/cbse/class-12/chemistry/chapters) - [Start free →](https://www.swavid.com/signup)