Chemical Bonding is a fixed 1–2 questions in JEE Main and NEET. Most questions are ‘find the shape / hybridisation / bond order’ — and each has a 20-second shortcut.
Hybridisation shortcut
Steric number = (valence electrons of central atom + number of monovalent atoms attached ± charge)/2. 2 → sp, 3 → sp², 4 → sp³, 5 → sp³d, 6 → sp³d², 7 → sp³d³. (Add for negative charge, subtract for positive.)
Example: NH₄⁺ → (5 + 4 − 1)/2 = 4 → sp³. SF₆ → (6 + 6)/2 = 6 → sp³d². XeF₄ → (8 + 4)/2 = 6 → sp³d², 2 lone pairs → square planar.
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VSEPR shapes
| Bond pairs, lone pairs | Shape | Example |
|---|---|---|
| 2, 0 | Linear | BeCl₂, CO₂ |
| 3, 0 | Trigonal planar | BF₃ |
| 2, 1 | Bent | SO₂ |
| 4, 0 | Tetrahedral | CH₄ |
| 3, 1 | Pyramidal | NH₃ |
| 2, 2 | Bent | H₂O |
| 5, 0 | Trigonal bipyramidal | PCl₅ |
| 4, 1 | See-saw | SF₄ |
| 3, 2 | T-shape | ClF₃ |
| 2, 3 | Linear | XeF₂, I₃⁻ |
| 6, 0 | Octahedral | SF₆ |
| 4, 2 | Square planar | XeF₄ |
MOT bond order
- Bond order = (Nb − Na)/2
- Order up to N₂ (≤14 e⁻): σ1s σ*1s σ2s σ*2s π2px=π2py σ2pz …; from O₂ onward σ2pz comes before π2p
- O₂ = 2 (paramagnetic), O₂⁺ = 2.5, O₂⁻ = 1.5, N₂ = 3, He₂ = 0 (does not exist)
- Stability ∝ bond order; bond length ∝ 1/bond order
Other quick rules
- Dipole moment zero for symmetric molecules: CO₂, BF₃, CCl₄, trans isomers
- Fajan: small cation + large anion → more covalent (LiI more covalent than LiF)
- H-bonding: intramolecular in o-nitrophenol (lower b.p.), intermolecular in p-nitrophenol
Common mistakes
- Counting lone pairs of the outer atoms instead of the central atom
- Using the pre-O₂ MO order for O₂ and F₂
- Assuming polar bonds always make a polar molecule
Related: Complex numbers for JEE.
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Frequently asked questions
Is this Chemical Bonding content at JEE/NEET level?
Yes. It covers the formulas, facts and question types that appear in JEE Main, JEE Advanced and NEET, with the NCERT base that these exams follow.
How many questions come from Chemical Bonding?
Typically one to three questions per paper, depending on the year. Check the chapter-wise weightage post and give this topic time in proportion.
Where can I get chemical bonding doubts solved quickly?
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