Chemical Bonding and Molecular Structure for NEET UG
Why do atoms join, and why do molecules have the shapes they do? Lewis structures, VSEPR, hybridisation and molecular orbital theory explain it step by step.
ChemistryClass 1172 MCQs4 lessons14 flashcards4 memory tricks
Practise Chemical Bonding and Molecular Structure free
What you'll learn
- Ionic and covalent bonds, and formal charge
Draw Lewis structures, apply the octet rule and calculate formal charge. - VSEPR theory and molecular shapes
Predict the shape and bond angle of a molecule from its electron pairs. - Hybridisation
Find the hybridisation of the central atom and link it to geometry. - Molecular orbital theory and bond order
Fill MO diagrams for diatomic molecules and find bond order and magnetic behaviour.
Key formulas
| Formal charge | FC = valence electrons − non-bonding electrons − ½(bonding electrons) |
|---|---|
| Bond order | BO = ½(bonding electrons − antibonding electrons) |
Memory tricks
lp–lp > lp–bp > bp–bp. Each lone pair squeezes the bond angle: CH₄ 109.5°, NH₃ 107°, H₂O 104.5°.
Hydrogen bonds form when H is bonded to F, O or N. That's why water is a liquid at room temperature while H₂S is a gas.
Steric number 2, 3, 4, 5, 6 → sp, sp², sp³, sp³d, sp³d² → linear, trigonal planar, tetrahedral, trigonal bipyramidal, octahedral.
Bond order = (bonding − antibonding)/2: O₂⁺ 2.5, O₂ 2, O₂⁻ 1.5, O₂²⁻ 1. Higher bond order means a shorter, stronger bond. O₂ is paramagnetic (two unpaired electrons).
Try 3 NEET-style questions
Q1. Hydrogen fluoride (HF) exists as zig-zag chains in the solid and liquid state because of
- intramolecular hydrogen bonding
- ionic bonding
- intermolecular hydrogen bonding
- metallic bonding
Show answer
Answer: (3) intermolecular hydrogen bonding
HF molecules are linked by intermolecular hydrogen bonds between H of one molecule and F of another, forming zig-zag chains.
Q2. Which molecule has a linear shape?
- H₂O
- SO₂
- NH₃
- CO₂
Show answer
Answer: (4) CO₂
CO₂ (O=C=O) is linear. H₂O and SO₂ are bent; NH₃ is pyramidal.
Q3. The shape of the BF₃ molecule, according to VSEPR theory, is
- trigonal pyramidal
- T-shaped
- tetrahedral
- trigonal planar
Show answer
Answer: (4) trigonal planar
B in BF₃ has three bond pairs and no lone pair. The bond pairs arrange themselves in a trigonal planar shape with 120° angles (sp² hybridisation).
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