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Chemical Bonding: concepts, formulas & solved PYQ-style examples

Chemical bonding is the backbone of inorganic and organic chemistry and is asked regularly. Most questions test shapes, hybridisation, bond order and magnetic behaviour.

Count bond pairs and lone pairs around the central atom first — shape and hybridisation follow directly.

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Key concepts

VSEPR theory

Lone pairs repel more than bond pairs, distorting ideal geometries.

Hybridisation

Steric number 2→sp, 3→sp², 4→sp³, 5→sp³d, 6→sp³d².

Molecular orbital theory

Bond order and magnetism of O₂, N₂ and their ions.

Dipole moment

Symmetric shapes cancel bond dipoles (CO₂, BF₃, CCl₄).

Hydrogen bonding

Explains high boiling points and solubility trends.

Formula sheet

Steric number

SN=bond pairs+lone pairs\text{SN} = \text{bond pairs} + \text{lone pairs}

Bond order

B.O.=12 (Nb−Na)\text{B.O.} = \tfrac12\,(N_b - N_a)

Formal charge

FC=V−L−12BFC = V - L - \tfrac12 B

Dipole moment

μ=q×d\mu = q \times d

What PYQs keep asking

Patterns that repeat across previous-year JEE and NEET papers for this chapter.

  • Shape and hybridisation of species like SF₄, ClF₃, XeF₄, XeF₂ and I₃⁻.
  • Bond order, bond length and magnetism of O₂, O₂⁺, O₂⁻, N₂ and their ions.
  • Which molecule has zero dipole moment.
  • Comparing bond angles (NH₃ vs H₂O vs CH₄).

Solved examples

Example 1

Give the hybridisation and shape of SF₄ and XeF₄.

  1. 1SF₄: S has 4 bond pairs + 1 lone pair, steric number 5 → sp³d; the lone pair sits equatorial, giving a see-saw shape.
  2. 2XeF₄: Xe has 4 bond pairs + 2 lone pairs, steric number 6 → sp³d²; the lone pairs sit opposite each other.
  3. 3Leaving 4 F atoms in one plane gives a square planar shape.
Answer: SF₄: sp³d, see-saw · XeF₄: sp³d², square planar
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Example 2

Arrange O₂, O₂⁺ and O₂⁻ in increasing order of bond length.

  1. 1From MOT: O₂ has bond order 2 (two unpaired electrons, paramagnetic).
  2. 2Removing an antibonding electron gives O₂⁺ bond order 2.5; adding one gives O₂⁻ bond order 1.5.
  3. 3Higher bond order means a shorter bond.
Answer: O₂⁺ < O₂ < O₂⁻
Watch a whiteboard video solution of this example →

Common traps

  • Forgetting lone pairs on the central atom when predicting shape.
  • Calling O₂ diamagnetic — MOT shows two unpaired electrons.
  • Assuming every polar bond makes the whole molecule polar.

Practise with

General Organic Chemistry (GOC)Chemical ThermodynamicsElectrochemistryMolecular shapes (VSEPR) simulation2 Chemical Bonding practice questionsVideo solutions

FAQ

How do I find hybridisation quickly?

Count bond pairs plus lone pairs on the central atom (steric number): 2 sp, 3 sp², 4 sp³, 5 sp³d, 6 sp³d².

Why is O₂ paramagnetic?

In molecular orbital theory its two highest electrons occupy two degenerate π* orbitals singly, leaving two unpaired electrons.

Is chemical bonding asked in NEET?

Yes — shapes, hybridisation, bond order and dipole moment are asked very often.

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