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Covalent bond
Class 11 | Chemistry
Definition
A covalent bond is sharing of electrons between atoms to achieve stable electronic configuration.
Types
Single, Double, Triple, Coordinate covalent bond.
Characteristics
Usually low melting and boiling points (except network solids), poor electrical conductivity, often soluble in non-polar solvents.
Classification based on Electronegativity
Non-polar: negligible ΔEN (H₂, Cl₂). Polar: moderate ΔEN with partial charges (HCl, H₂O, NH₃).
Lewis Representation of Simple Molecules
Dot-and-cross structures for shared pairs (e.g., H₂O: two bonding pairs + two lone pairs on O).
Variable Covalency and Its Reason
Elements with vacant d-orbitals (P, S, Cl) can expand the octet → multiple valencies (PCl₃ vs PCl₅, SF₆).
Formal Charge
FC = Valence e⁻ − (Nonbonding e⁻ + ½×Bonding e⁻); used to judge the most stable resonance form.
Bond Parameters
Bond length (triple < double < single); Bond angle (CH₄ 109.5°, NH₃ 107°, H₂O 104.5°); Bond enthalpy (triple > double > single); Bond order (integer or fractional with resonance).
Limitations of Octet Rule / Deviations
Incomplete octet (BeCl₂, BF₃); Expanded octet (SF₆, PCl₅); Odd-electron species (NO, NO₂).
