Introduction
Chemical bonding is the process by which atoms combine to form molecules. The force that holds atoms or ions together within a molecule is called a chemical bond. Atoms combine to achieve a state of minimum energy and maximum stability, acquiring the stable electron configuration of the nearest noble gas.
Chemical Bond is the force that holds atoms or ions together within a molecule. The process of their combination is called Chemical Bonding.
Types of Chemical Bonds
Bond Formation Based on Atom Types
| Atoms Involved | Bond Type |
|---|---|
| A + B (Metal + Non-metal) | Electrovalent |
| B + B (Non-metal + Non-metal) | Covalent |
| A + A (Metal + Metal) | Metallic |
| Lewis acid + Lewis base | Coordinate/Hydrogen |
Electrovalent (Ionic) Bond
Formation Conditions
Characteristics of Ionic Compounds
Covalent Bond
Formation Conditions
Characteristics of Covalent Compounds
Variable Covalency
Elements like P, S, Cl, Br, I show variable covalency due to vacant d-orbitals. Elements H, N, O, F do not have d-orbitals and thus don't show variable valency.
Sigma (σ) vs Pi (π) Bonds
Hybridization
Hybridization is the intermixing of dissimilar orbitals of the same atom having slightly different energies to form new orbitals of equal energies and identical shapes.
Characteristics
Determining Hybridization
Where:
H = Number of orbitals in hybridization
V = Valence electrons of central atom
M = Number of monovalent atoms
C = Charge on cation
A = Charge on anion
| H Value | Hybridization | Geometry |
|---|---|---|
| 2 | sp | Linear |
| 3 | sp² | Trigonal planar |
| 4 | sp³ | Tetrahedral |
| 5 | sp³d | Trigonal bipyramidal |
| 6 | sp³d² | Octahedral |
VSEPR Theory
Valence Shell Electron Pair Repulsion theory states that electron pairs (bonded or lone) around a central atom arrange themselves to minimize repulsion.
Repulsion order: lp-lp > lp-bp > bp-bp (where lp = lone pair, bp = bond pair)
Molecular Geometry
| Type | Bond Pairs | Lone Pairs | Geometry | Examples |
|---|---|---|---|---|
| AX₂ | 2 | 0 | Linear | CO₂, BeCl₂ |
| AX₃ | 3 | 0 | Trigonal planar | BF₃, SO₃ |
| AX₂E | 2 | 1 | Bent | SO₂, SnCl₂ |
| AX₄ | 4 | 0 | Tetrahedral | CH₄, CCl₄ |
| AX₃E | 3 | 1 | Trigonal pyramidal | NH₃, PCl₃ |
| AX₂E₂ | 2 | 2 | Bent | H₂O, H₂S |
Important Points to Remember
Key Points for JEE Main
- Ionic compounds conduct electricity only in molten state or solution
- Covalent bonds are directional while ionic bonds are non-directional
- Bond strength: Triple > Double > Single
- Bond length: Single > Double > Triple
- Dipole moment helps determine molecular polarity and geometry
- Resonance increases stability and makes bond lengths equal
- Hydrogen bonding explains abnormal properties of H₂O, HF, NH₃
Do's
Don'ts
JEE Main Weightage
This chapter typically carries 3-4 questions in JEE Main, making it a very high-weightage chapter. Questions often focus on bond types, VSEPR theory, hybridization, and molecular orbital theory.