Class 12 Chemistry Coordination Compounds Formula Sheet PDF

Ans. You can download the Coordination Compounds Class 12 Chemistry Formula Sheet PDF directly from this Collegedunia page. Both the Normal and HD versions are available and free.

Ans. Yes. This page reflects the current 2026-27 syllabus for Class 12 Chemistry. The Coordination Compounds chapter is fully retained in the new edition with no formula cuts; every relation in Sections 5.1 to 5.8 of the NCERT remains examinable.

Ans. The Formula Sheet PDF runs approximately 8 pages and covers the master formula table, symbol glossary, CFSE configuration reference, quick-fact MCQ cards, when-to-use decision tree, and four common numerical pattern templates.

Ans. The crystal field stabilisation energy of an octahedral complex is CFSE = [-0.4 n(t_2g) + 0.6 n(e_g)] Δ_o + xP, where n(t_2g) and n(e_g) are the electrons in the lower and higher d-orbital sets and xP is the energy cost of x extra electron pairs formed (relative to the free ion).

Ans. EAN (Effective Atomic Number) = Z(M) - OS(M) + 2 x CN, where Z(M) is the atomic number of the central metal, OS is its oxidation state, and CN is the coordination number. For [Ni(CO)₄], EAN = 28 - 0 + 8 = 36 (Kr config), justifying the high stability.

Ans. For the same metal, ligands and bond distances, Δ_t = (4/9) Δ_o ≈ 0.45 Δ_o. Tetrahedral geometry has only 4 ligands (vs 6) and none of them sits directly along the d-orbital lobes, so the splitting is smaller. Consequently Δ_t never exceeds the pairing energy P, and tetrahedral complexes are always high spin.

Ans. The series ranks ligands by the Δ_o they produce: I^- < Br^- < Cl^- < F^- < OH^- < H₂O < NH₃ < en < NO₂^- < CN^- < CO. Strong-field ligands at the right end (CN^-, CO, en, NO₂^-) drive low-spin configurations; weak-field ligands at the left end (halides, water) keep complexes high spin.

Ans. Coordination compounds show structural isomerism (ionisation, hydrate, linkage, coordination) and stereoisomerism (geometrical cis-trans and fac-mer, optical Δ / Λ). [Co(NH₃)₄Cl₂]⁺ shows cis-trans; [Co(en)₃]³⁺ shows optical activity; NO₂^- vs ONO^- gives linkage isomers.

Ans. The spin-only magnetic moment is μ = √n(n+2) BM, where n is the number of unpaired d-electrons in the metal ion after considering the ligand field. Quick values: n = 1 gives 1.73 BM, n = 2 gives 2.83 BM, n = 3 gives 3.87 BM, n = 4 gives 4.90 BM, n = 5 gives 5.92 BM. Always classify the ligand as strong or weak field first, then count unpaired electrons.

Ans. Primary valence equals the oxidation state of the central metal, is ionisable, and is satisfied by anions outside the coordination sphere. Secondary valence equals the coordination number, is non-ionisable, satisfied by ligands inside the sphere, and is directional - it fixes the geometry. In [Co(NH₃)₅Cl]Cl₂, Co³⁺ has primary valence 3 and secondary valence 6.

Ans. The chelate effect is the extra thermodynamic stability of complexes formed by polydentate (chelating) ligands compared to monodentate-only analogues. The driver is entropy: replacing two monodentate ligands with one bidentate ligand releases free water molecules into the bulk, raising disorder. [Ni(en)₃]²⁺ is about 10⁵ times more stable than [Ni(NH₃)₆]²⁺; EDTA^4- sequesters Pb²⁺ and Hg²⁺ in heavy-metal therapy through five chelate rings.

Ans. Metal carbonyls have a two-way bond. The C lone pair of CO donates into an empty metal hybrid orbital ( σ donation), and a filled metal d-orbital donates back into the empty π^* anti-bonding orbital of CO ( π back-bonding). Back-donation strengthens the M-C bond and weakens the C-O bond, dropping the C-O stretching frequency from 2143 cm^-1 in free CO to roughly 2050 cm^-1 in Ni(CO)₄. Ni(CO)₄ uses sp³ hybridisation, is tetrahedral and diamagnetic, with EAN = 36.

Ans. Haemoglobin is an Fe²⁺-porphyrin complex that binds O₂ reversibly. Chlorophyll is the Mg²⁺-porphyrin (chlorin) that drives photosynthesis. Vitamin B₁₂ (cyanocobalamin) is a Co³⁺-corrin complex with CN^- as the sixth ligand. Cisplatin (cis-[Pt(NH₃)₂Cl₂]) is the platinum anticancer drug; only the cis isomer cross-links with DNA. EDTA chelates lead and mercury in heavy-metal therapy.