Molecular Structure and Bonding

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Course Objectives:

This course will enable the students to -

  1. Provide an in-depth knowledge about different types of bonding in main group elements
  2. Acquaint the students with the concept of hybridization and geometry of covalent molecules, shapes of atomic and molecular orbitals.

Course Outcomes (COs):


Learning outcomes

  (at course level)

Learning and teaching strategies

Assessment Strategies

Paper Code

  Paper Title




Molecular Structure and Bonding


The students will be able to –

CO1: calculate the radius ratio of ionic molecules and determine the ionic structures of the type AX and AX2 

CO2: apply the concept of Born Haber cycle in predicting the lattice energy, ionization energy and stability of the ionic compounds.

CO3: differentiate the types of defects in solids.

CO4: describe the various types of hybridization and geometry of molecules.

CO5: construct molecular orbital diagrams of homo and hetero nuclear diatomic molecules and determine the bond order with the help of M.O. diagram

CO6: discuss the different theories of metallic bonding  and distinguish between types of Van der Waals interaction

CO7: explain types, properties, theories of H-bonding and its effect on physical properties.

Class lectures


Group discussions

Peer teaching and learning


The oral and written examinations (Scheduled and surprise tests)

Problem-solving exercises



Semester End Examination




Unit I: 
The Ionic Bond

Introduction, size effects, radius ratio rules- Calculation of limiting radius ratio values for coordination number 3,4 ,6 and 8; Close packing; classification of ionic structures, (ionic compounds of the type AX (ZnS, NaCl, CsCl) and AX2 (CaF2-Fluorite)), limitations of radius ratio rule; Calculation of lattice energy, factors affecting lattice energy; the Born Haber cycle and its application; solvation energy and solubilities of ionic substances; stoichiometric and non-stoichiometric defects.


Unit II: 
The Covalent Bond

The Lewis theory, octet rule, explanations for the failure of octet rule,exceptions to octet rule, valence bond theory (Heitler and London approach) and its limitations; resonance,directional character of covalent bond, various types of hybridization ( sp, sp2, sp3, sp3d,sp3d2, dsp2, sp3d3) and shapes of molecules; VSEPR theory,  isoelectronic principle, examples using VSEPR theory, polarizability of ions, Fajans’ rule and consequences of polarization, dipole moment and percentage ionic character in covalent compounds (electronegativity difference and dipole moment method), bond energy and bond length.



Unit III: 
Molecular Orbital Approach in Covalent Bond

Introduction, LCAO approach, combination of orbitals (s-s, s-p, p-p, non-bonding combination of orbitals), examples of molecular orbital treatment for homonuclear diatomic molecules– H2+, H2, He2, B2, C2, N2, Be2, O2, O2+1, O2-1, O2-2, F2, examples of molecular orbital treatment for heteronuclear diatomic molecules - NO, NO+, CO, CO+, CO-,  CN, CN-  molecule, comparison of VBT and MOT.



Unit IV: 
The Metallic Bond

Multicentered bonding in electron deficient molecule,general properties of metals– conductivity, lusture, malleability, ductility, crystal structures; theories of bonding in metals – Free electron theory, valence bond theory and band theory – Conductors, insulators and semi-conductors,superconductors.



Unit V: 
Weak Interactions

VanderWaals forces: Ion-dipole forces, dipole-dipole interactions, induced dipole interactions, instantaneous dipole – induced dipole interactions, repulsive forces.

Hydrogen bond: Types, theories and properties of H-bond, effects of H-bond on physical properties.



Essential Readings: 
  • Concise Inorganic Chemistry; Fifth Edition; J.D. Lee; Wiley India(P) Ltd, New Delhi, 2008.
  • Inorganic Chemistry; Seventh International Edition; M. Weller, T. Overton, J. Rourke, F. Armstrong; OxfordUniversity Press, New York, 2018.


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