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ChemistryMediumClass 12

VBT โ€” Hybridization, inner/outer orbital complexes

Coordination Compounds

15

JEE Qs

8%

Hard

75

min

Systematically determine oxidation state, d-electron count, ligand type (strong/weak field), electron pairing, hybridization, geometry, and finally magnetic nature to avoid errors.

๐Ÿงฎ Key Formulas

ฮผ = sqrt(n(n+2))
Coordination Number 4 -> sp3 (Tetrahedral) or dsp2 (Square planar)
Coordination Number 6 -> sp3d2 (Octahedral, Outer orbital) or d2sp3 (Octahedral, Inner orbital)

โœ… Key Points for JEE

  • 1Valence Bond Theory (VBT) explains the geometry and magnetic properties of coordination compounds based on hybridization and orbital overlap.
  • 2The oxidation state of the central metal ion must be correctly determined to find its d-electron configuration.
  • 3Ligands are classified as strong field or weak field based on their ability to cause electron pairing in the d-orbitals of the central metal ion.
  • 4Strong field ligands (e.g., CN-, CO, NH3 for Co3+) lead to pairing of electrons in d-orbitals, resulting in inner orbital (d2sp3) and low spin complexes.
  • 5Weak field ligands (e.g., H2O, F-, Cl-) generally do not cause electron pairing, leading to outer orbital (sp3d2) and high spin complexes.

โš ๏ธ Common Mistakes

  • โœ•Incorrectly identifying the oxidation state of the central metal, leading to a wrong d-electron configuration.
  • โœ•Failing to recognize strong vs. weak field ligands, which determines whether electron pairing occurs.
  • โœ•Incorrectly applying electron pairing rules, especially for d4, d5, d6, and d7 configurations.
  • โœ•Confusing inner orbital/outer orbital with low spin/high spin; while often correlated, they describe different aspects.

๐Ÿ“ Practice Questions

See all

Q74.In the Claisen-Schmidt reaction to prepare, dibenzalacetone from 5.3 g of benzaldehyde, a total of 3.51 g of product was obtained. The percentage yield in this reaction was ______ %.

2025ยทNumericalHard

Q61.The calculated spin-only magnetic moments of K3 [Fe(OH)6] and K4 [Fe(OH)6] respectively are : (1) 3.87 and 4.90 B.M. (2) 4.90 and 5.92 B.M. (3) 4.90 and 4.90 B.M. (4) 5.92 and 4.90 B.M.

2025ยทMCQMedium

Q54.Identify the homoleptic complexes with odd number of d electrons in the central metal : (A) [FeO4]2โˆ’ (B) [Fe(CN)6]3โˆ’ (C) [Fe(CN)5NO]2โˆ’ (D) [CoCl4]2โˆ’ (E) [Co(H2O)3 F3] Choose the correct answer from the options given below : (1) (A), (B) and (D) only (2) (C) and (E) only (3) (B) and (D) only (4) (A), (C) and (E) only

2025ยทMCQMedium

Q68.In which of the following complexes the CFSE, ฮ”o will be equal to zero? (1) [Fe(en)3]Cl3 (2) K4 [Fe(CN)6] (3) [Fe(NH3)6]Br2 (4) K3 [Fe(SCN)6]

2025ยทMCQMedium

Q70.From the magnetic behaviour of [NiCl4]2โˆ’ (paramagnetic) and [Ni(CO)4] (diamagnetic), choose the correct geometry and oxidation state. (1) [NiCl4]2โˆ’: NiII , tetrahedral [Ni(CO)4] : NiII , (2) [NiCl4]2โˆ’ : NiII , square planar [Ni(CO)4] : Ni(0) square planar , square planar (3) [NiCl4]2โˆ’: NiII , tetrahedral [Ni(CO)4] : Ni(0), (4) [NiCl4]2โˆ’: Ni(0), tetrahedral [Ni(CO)4] : Ni(0), tetrahedral square planar

2025ยทMCQHard

Q53.The correct order of the following complexes in terms of their crystal field stabilization energies is : (1) [Co(NH3)4]2+ < [Co(NH3)6]2+ < [Co(en)3]3+ < [Co(NH3)6]3+ (2) [Co(NH3)6]2+ < [Co(NH3)6]3+ < [Co(NH3)4]2+ < [Co(en)3]3+ (3) [Co(en)3]3+ < [Co(NH3)6]3+ < [Co(NH3)6]2+ < [Co(NH3)4]2+ (4) [Co(NH3)4]2+ < [Co(NH3)6]2+ < [Co(NH3)6]3+ < [Co(en)3]3+

2025ยทMCQHard

NCERT Chapters

  • Class 11 Chemistry Ch 4: Chemical Bonding and Molecular Structure
  • Class 12 Chemistry Ch 9: Coordination Compounds