Chemical Bonding

This is the "Grammar" of chemistry. It explains how atoms connect to form molecules. If you master VSEPR Theory and Hybridization, Organic Chemistry will make much more sense later.

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⚠️ Prerequisites

Periodic Trends: Electronegativity differences (Ionic vs Covalent).
Valence Electrons: Knowing group numbers (e.g., Nitrogen has 5 valence electrons).
Orbitals: Shapes of s and p orbitals.

🧠 Study Approach

Visual & Spatial: You must be able to visualize 3D shapes in your head (Tetrahedral, Trigonal Bipyramidal). Practice drawing structures daily until it becomes muscle memory.

Study Sequence

1. Ionic Bond & Lattice Energy

Kossel-Lewis approach. Octet Rule limitations (Incomplete/Expanded octet). Factors affecting Lattice Enthalpy (Charge/Size).

2. Covalent Bond & Fajan's Rule

Lewis Structures. Formal Charge. Fajan's Rule: Smaller cation + Larger anion = More Covalent Character (Polarization).

3. VSEPR Theory (CRITICAL)

Valence Shell Electron Pair Repulsion. Distinguish between Geometry (arrangements of pairs) and Shape (atoms only). Effect of Lone Pairs on bond angles. ($lp-lp > lp-bp > bp-bp$).

4. Valence Bond Theory & Hybridization

Sigma ($\sigma$) vs Pi ($\pi$) bonds. Concept of Hybridization ($sp, sp^2, sp^3, sp^3d, sp^3d^2$). Calculating hybridization number ($Z$) to predict geometry.

5. Molecular Orbital Theory (MOT)

LCAO. Bonding (BMO) vs Antibonding (ABMO). Filling order for $O_2$ vs $N_2$. Calculating Bond Order. Magnetic nature (Why $O_2$ is paramagnetic).

6. Dipole Moment & Hydrogen Bonding

Vector addition of dipoles (e.g., $NF_3$ vs $NH_3$). Intermolecular vs Intramolecular H-bonding and effect on boiling points.

🎯 How to Practice

Drawing: Draw Lewis structures for 5 molecules daily ($PCl_5, SF_6, XeF_4, ClF_3, H_2O$). Identify lone pairs and predict the shape.

MOT Diagrams: Practice drawing energy level diagrams for $N_2$ and $O_2$. Memorize the change in orbital sequence for molecules with >14 electrons.

Compare Angles: Don't just memorize angles. Understand why bond angle of $CH_4 > NH_3 > H_2O$ (Lone pair compression).

📝 Quick Revision Formulas

Hybridization Number (Z) $$Z = \frac{1}{2}(V + M - C + A)$$

V: Valence $e^-$, M: Monovalent atoms, C/A: Charge

Bond Order (MOT) $$B.O. = \frac{1}{2}(N_b - N_a)$$

$N_b$: Bonding electrons, $N_a$: Antibonding electrons

Dipole Moment $$\mu = q \times d \quad (\text{Debye})$$

$O_2$ is paramagnetic (2 unpaired $e^-$).
Lone pairs occupy equatorial positions in TBP geometry.

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Lesson Plan: Chemical Bonding