Ionic, Covalent and Metallic Bonding
Ionic bonding (metal + non-metal)
Electrons are transferred: the metal loses electrons (forms a + ion); the non-metal gains them (forms a − ion). Opposite charges attract strongly.
- Forms giant ionic lattices.
- High melting/boiling points (strong electrostatic forces).
- Conduct electricity only when molten or dissolved (ions free to move).
Example: Na → Na⁺ + e⁻, Cl + e⁻ → Cl⁻ → NaCl.
Covalent bonding (non-metal + non-metal)
Atoms share pairs of electrons.
- Simple molecules (H₂O, CO₂, Cl₂): low melting points (weak forces between molecules), don't conduct.
- Giant covalent (diamond, graphite, silicon dioxide): very high melting points.
Metallic bonding (metals)
A lattice of positive ions in a sea of delocalised electrons.
- High melting points, good conductors (free electrons), malleable (layers slide).
Summary
| Bonding | Particles | Conducts? | Melting point |
|---|---|---|---|
| Ionic | + and − ions | When molten/dissolved | High |
| Simple covalent | molecules | No | Low |
| Metallic | ions + free e⁻ | Yes | High |
Exam tip
Ionic compounds conduct only when molten or in solution because the ions must be free to move — a very common exam point.