Formation of Ionic Bonds
Ionic bonds form when a metal atom transfers electrons to a non-metal atom, forming oppositely charged ions that attract each other.
Ionic bonding: the electrostatic force of attraction between oppositely charged ions formed by the transfer of electrons from a metal to a non-metal.
Formation of NaCl:
- Sodium: 2,8,1 → loses 1 electron → Na⁺ (2,8) — noble gas configuration of Ne
- Chlorine: 2,8,7 → gains 1 electron → Cl⁻ (2,8,8) — noble gas configuration of Ar
- Na⁺ and Cl⁻ attract each other → ionic bond
Formation of MgO:
- Magnesium: 2,8,2 → loses 2 electrons → Mg²⁺ (2,8)
- Oxygen: 2,6 → gains 2 electrons → O²⁻ (2,8)
Dot-and-cross diagrams for ionic compounds:
- Show outer shell electrons only
- Transfer is shown by dots and crosses from different atoms
- Square brackets around each ion with charge outside
Deducing ionic formulae:
- Balance charges so the compound is electrically neutral
- Mg²⁺ + 2Cl⁻ → MgCl₂ (2 chloride ions balance one magnesium ion)
- Al³⁺ + 3OH⁻ → Al(OH)₃
- Metal loses electrons (cation); non-metal gains electrons (anion). Both achieve noble gas config.
- Ionic bond = electrostatic attraction between oppositely charged ions.
- Formula: balance ion charges to make neutral compound (Mg²⁺ + 2Cl⁻ → MgCl₂).