a) What is meant by the term "ionic bond"? [1] b) Write the characteristics of ionic bonds. [2] c) Write the examples of ionic compounds. [2]

a) Meaning of Ionic Bond

An ionic bond is a type of chemical bond formed between two atoms (or groups of atoms) by the complete transfer of electrons from one atom to another. This transfer results in the formation of positively charged cations (electron donors, usually metals) and negatively charged anions (electron acceptors, usually non-metals). The electrostatic force of attraction between these oppositely charged ions holds them together in a stable lattice structure.

structure

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b) Characteristics of Ionic Bonds

Ionic bonds exhibit the following key characteristics:

1. Electron Transfer

   • Electrons are completely transferred from a metal (low ionization energy) to a non-metal (high electron affinity).
   • Example: Sodium (Na) loses 1 electron to form Na⁺, while chlorine (Cl) gains 1 electron to form Cl⁻.

2. Formation of Ions

   • The resulting ions have stable electronic configurations (usually noble gas configurations).
   • Cations are smaller than their parent atoms, while anions are larger (due to increased electron-electron repulsion).

3. Electrostatic Attraction

   • The bond arises from the strong Coulombic attraction between oppositely charged ions.
   • The bond strength depends on the magnitude of charges and the distance between ions (lattice energy).

4. Physical Properties

   • High Melting and Boiling Points: Strong ionic forces require significant energy to break.
   • Solubility in Polar Solvents: Ionic compounds dissolve in water (a polar solvent) due to ion-dipole interactions.
   • Electrical Conductivity: Conduct electricity in molten or aqueous states (ions are free to move) but not in solid state (ions are fixed in a lattice).
   • Brittleness: Ionic crystals shatter when stressed due to repulsion between like-charged ions.

5. Lattice Structure

   • Ionic compounds form crystalline solids with a regular, repeating 3D lattice (e.g., NaCl adopts a face-centered cubic structure).

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c) Examples of Ionic Compounds

Ionic compounds are typically formed between metals (Group 1, 2) and non-metals (Group 16, 17). Common examples include:

H₂OH₂OCuSO₄

Additional Notes:

• Polyatomic Ions: Some ionic compounds contain polyatomic ions (e.g., CO₃²⁻, NO₃⁻, SO₄²⁻), such as CaCO₃ (calcium carbonate) or NaNO₃ (sodium nitrate).
• Hydrated Ionic Compounds: Examples include CuSO₄·5H₂O (copper(II) sulphate pentahydrate), where water molecules are incorporated into the crystal lattice.

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Na+Cl₂Electron transfer → Ionic bond formationStrong electrostatic attraction between oppositely charged i2NaCl+energy