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Chemistry · Class 9 · Chapter 4: Chemical Bonding

8 min

Key points

Chemical bond is the force of attraction that holds atoms together in a molecule or compound
Ionic bond forms between metal and non-metal atoms through complete transfer of electrons
Covalent bond forms between non-metal atoms through sharing of electrons
Electronegativity difference determines the type of bond: >1.7 ionic, <1.7 covalent
Lewis dot structure shows valence electrons as dots around atomic symbols
Coordinate covalent bond forms when one atom provides both electrons for sharing
Metallic bonding occurs in metals through sea of delocalized electrons
Bond length is the distance between nuclei of two bonded atoms
Lattice energy is the energy required to completely separate one mole of ionic solid into gaseous ions

Definitions

Chemical Bond: Chemical bond is the force of attraction that holds atoms together in a molecule or compound.
Ionic Bond: Ionic bond is formed by the complete transfer of electrons from metal atom to non-metal atom resulting in the formation of ions.
Covalent Bond: Covalent bond is formed by the mutual sharing of electrons between two non-metal atoms.
Electronegativity: Electronegativity is the tendency of an atom to attract shared electrons towards itself in a covalent bond.
Coordinate Covalent Bond: Coordinate covalent bond is formed when both electrons of the shared pair are contributed by one atom only.

Worked example

Define chemical bonding and explain how sodium chloride (NaCl) is formed through ionic bonding. (6 marks)

Chemical bonding is the force of attraction that holds atoms together in molecules or compounds. Sodium has electronic configuration (2,8,1) and chlorine has (2,8,7). To achieve stable octet configuration, sodium loses one electron to form Na⁺ ion (2,8) and chlorine gains one electron to form Cl⁻ ion (2,8,8). The electrostatic force of attraction between oppositely charged Na⁺ and Cl⁻ ions forms ionic bond, resulting in ionic compound sodium chloride (NaCl).

Common mistakes

Students confuse ionic and covalent bonds - remember ionic involves complete transfer, covalent involves sharing
Drawing incorrect Lewis dot structures - only show valence electrons as dots
Forgetting to mention electronegativity difference criteria for bond types
Not showing electron transfer clearly in ionic bond formation diagrams
Mixing up coordinate covalent bond definition with regular covalent bond

Quick recap

Chemical bonding is the attractive force holding atoms together. Ionic bonding occurs through electron transfer between metal and non-metal, forming oppositely charged ions. Covalent bonding involves electron sharing between non-metals. Atoms bond to achieve stable electronic configuration (usually octet rule).

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