AITestSeriesAITestSeries
Syllabus
🚀 IIT JEE
Subject:Chemistry Syllabus Structure

Chemical Bonding

Syllabus Unit: Physical Chemistry

Why it matters

Chapter overview

Chemical bonding explains why atoms combine at all and predicts the exact 3D shape, polarity and strength of the result. This topic runs from the electrostatic simplicity of ionic and covalent bonds, through VSEPR's geometric predictions and the hybridisation model of orbital overlap, to the quantitative bond parameters — dipole moment, bond length, bond order and bond enthalpy — that JEE tests relentlessly across inorganic and organic chemistry alike.

Chemistry Syllabus Structure Physical Chemistry ~33% weightage
Live Animation1 / 4
20
Nonpolar Covalent (ΔEN < 0.5)
55
Polar Covalent (0.5–1.7)
90
Ionic (ΔEN > 1.7)

1Ionic & Covalent Bonds

Every bond is a compromise between two extremes: complete electron transfer (ionic) and equal electron sharing (covalent).

Learning Objectives

  • State the octet rule and explain how ionic bonds form via complete electron transfer.
  • Predict lattice energy trends from ionic charge and radius using Coulomb's law intuition.
  • Distinguish covalent bond formation from ionic, and classify bonds as polar or nonpolar by electronegativity difference.
  • Define a coordinate (dative) covalent bond and identify one in NH4+.

Key Terms

Ionic BondElectrostatic attraction between oppositely charged ions formed by complete electron transfer, typically metal + nonmetal.
Lattice EnergyEnergy released forming one mole of ionic solid from gaseous ions; rises with higher ionic charge and smaller ionic radius.
Covalent BondA bond formed by the mutual sharing of one or more electron pairs between two atoms.
Coordinate (Dative) BondA covalent bond where both shared electrons come from a single donor atom, e.g. N's lone pair in NH4+.

Atoms bond to reach a lower-energy, more stable electron arrangement — usually one resembling a noble gas configuration (the octet rule). How that stability is reached splits bonds into two broad families.

Ionic bonds: transfer of electrons

  • Forms between atoms of large electronegativity difference — typically a metal and a nonmetal.
  • One or more electrons transfer completely, creating a cation and an anion held together purely by electrostatic (Coulombic) attraction.
  • Produces an extended crystal lattice, not discrete molecules — e.g. NaCl has no single 'NaCl molecule'.
Lattice Energy ∝ (q+ × q-) / (r+ + r-) — higher charges and smaller ionic radii give a stronger, higher-melting lattice.

Covalent bonds: sharing of electrons

  • Forms between atoms of small or no electronegativity difference — typically nonmetal-nonmetal.
  • Nonpolar covalent when ΔEN ≈ 0 (e.g. Cl2); polar covalent when ΔEN is moderate (e.g. HCl), creating partial charges δ+ and δ-.
Exam TipRule-of-thumb electronegativity guide: ΔEN < 0.5 → nonpolar covalent, 0.5–1.7 → polar covalent, > 1.7 → ionic. Useful for quick classification, though real bonding is a continuum, not three sharp boxes.

Coordinate (dative) bonds

In a coordinate bond, both electrons of the shared pair come from just one atom (the donor) into a vacant orbital on another (the acceptor) — e.g. NH3's lone pair bonds to H+ to form NH4+. Once formed, this bond is indistinguishable from an ordinary covalent bond.