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Chemical Bonding – Complete JEE Mains Revision

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Chemical Bonding – Complete JEE Mains Revision

Chemical bonding explains how atoms combine to form molecules and solids. JEE frequently tests exceptions, trends, geometry, and stability arguments.

1. Why Do Atoms Form Bonds?

Atoms form bonds to achieve lower potential energy and higher stability.

  • Noble gases → already stable
  • Others → bond to achieve octet / duplet

JEE Trap: Octet rule has many exceptions – it is NOT a universal law.

2. Types of Chemical Bonds

(a) Ionic (Electrovalent) Bond

  • Complete transfer of electrons
  • High lattice energy
  • High melting point

Lattice Energy: $$ U \propto \frac{z^+z^-}{r} $$

Repeated Question: Smaller ions + higher charge → stronger ionic bond

(b) Covalent Bond

  • Electron sharing
  • Directional
  • Low melting point (generally)

(c) Coordinate (Dative) Bond

Both electrons contributed by one atom. Example: $NH_4^+$, $H_3O^+$

3. Lewis Structures & Formal Charge

Formal Charge: $$ FC = V - L - \frac{B}{2} $$

  • Lower formal charge → higher stability
  • Negative FC prefers electronegative atom

4. VSEPR Theory (VERY HIGH YIELD)

Shape depends on repulsion between electron pairs:

Repulsion Order: $$ LP-LP > LP-BP > BP-BP $$

TypeExampleShape
AX₂BeCl₂Linear
AX₃BCl₃Trigonal planar
AX₄CH₄Tetrahedral
AX₃ENH₃Pyramidal
AX₂E₂H₂OBent

JEE Favorite: Lone pair compresses bond angle (NH₃ > H₂O)

5. Hybridisation

Hybridisation = mixing of atomic orbitals.

HybridGeometryExample
spLinearBeCl₂
sp²Trigonal planarBCl₃
sp³TetrahedralCH₄
sp³dTBPPCl₅
sp³d²OctahedralSF₆

Key Rule: Steric number = σ bonds + lone pairs

6. Valence Bond Theory (VBT)

  • Bond formed by orbital overlap
  • Greater overlap → stronger bond 

  • Orbital overlapping to form Sigma bond and pi bond.

σ bond → axial overlap π bond → sideways overlap

7. Molecular Orbital Theory (MOT)

Bond Order: $$ BO = \frac{N_b - N_a}{2} $$



  • BO > 0 → molecule exists
  • Higher BO → stronger bond

Repeated JEE Result: O₂ is paramagnetic (unpaired electrons)

8. Hydrogen Bonding

Occurs when H is bonded to N, O or F.

  • Intermolecular → high boiling point
  • Intramolecular → affects shape

Example: HF > HCl (boiling point)

9. Fajan’s Rule (Ionic vs Covalent Character)

Covalent character increases when:

  • Small cation
  • Large anion
  • High charge

Classic Order: LiI > LiBr > LiCl > LiF

10. Important Exceptions (JEE Loves These)

  • Incomplete octet → BF₃, BeCl₂
  • Expanded octet → SF₆, PCl₅
  • Odd electron → NO, NO₂
  • NH₃ more basic than PH₃ (lone pair availability)
  • Bond angle: NH₃ > PH₃ > AsH₃

11. Last-Day Formula Recall

  • $BO = (N_b - N_a)/2$
  • $FC = V - L - B/2$
  • Repulsion: LP-LP > LP-BP > BP-BP
  • Steric number = σ bonds + lone pairs

StudyBeacon Revision Series — concepts first, rank next.

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