JEE Main Chemical Bonding: Lewis Structures, VSEPR & Molecular Orbital Theory

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Chemical Bonding is tested in 2-3 JEE Main Chemistry questions and forms the conceptual backbone for both Organic and Inorganic Chemistry. A strong understanding here makes the rest of Chemistry easier.

Lewis Structures and Formal Charge

Draw Lewis structures: count valence electrons, arrange atoms, distribute electron pairs. Formal charge = valence electrons - nonbonding electrons - (bonding electrons/2). The structure with lowest formal charge is most stable. Resonance structures: resonance hybrid has intermediate properties.

VSEPR Theory and Shapes

Electron pair geometry depends on total pairs (bonding + lone). Molecular geometry depends on atom arrangement. Key shapes: linear (2 BP), trigonal planar (3 BP), tetrahedral (4 BP), trigonal bipyramidal (5 BP), octahedral (6 BP). Lone pairs compress bond angles.

Hybridization

sp³: 109.5°. sp²: 120°, one unhybridized p orbital. sp: 180°, two p orbitals form π system. Examples: CH₄ (sp³), C₂H₄ (sp²), C₂H₂ (sp). Be and B compounds can be sp² without fulfilling octet. Hybridization of central atom in H₂O, NH₃, PCl₅, SF₆.

Bond Parameters

Bond order ∝ bond strength ∝ 1/bond length. Bond dissociation energy trends. Polarity: electronegativity difference > 1.7 → ionic. Dipole moment: μ = q×d. JEE Main: determine if a molecule has dipole moment based on shape (CO₂ vs SO₂).

Molecular Orbital Theory (MOT)

Fill MOs in order: σ1s, σ*1s, σ2s, σ*2s, π2p, σ2p, π*2p, σ*2p. Bond order = (bonding - antibonding electrons)/2. Paramagnetic if unpaired electrons exist. O₂ is paramagnetic (BO=2, 2 unpaired). N₂ is diamagnetic (BO=3).

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