Chemical Bonding
Ionic, covalent and metallic bonding — structures and properties
Atoms bond to achieve a full outer electron shell (like noble gases).
Ionic bonding: Metal transfers electrons to non-metal. Forms **ions** with opposite charges that attract. Example: NaCl — Na loses 1e⁻ (Na⁺), Cl gains 1e⁻ (Cl⁻).
Covalent bonding: Non-metals share electrons. Forms molecules.
Metallic bonding: Sea of delocalised electrons surrounds positive metal ions. This explains: high melting points, electrical conductivity, malleability (layers can slide over each other).
Summary of properties:
| Bond type | Melting point | Conducts electricity? |
|-----------|-----------|-----------|
| Ionic | High | Yes (molten/dissolved) |
| Simple covalent | Low | No |
| Giant covalent | Very high | No (except graphite) |
| Metallic | High | Yes |
Key Points to Remember
- 1Ionic: metal loses, non-metal gains electrons
- 2Covalent: non-metals share electrons
- 3Giant covalent (diamond) has very high melting point
- 4Metallic: delocalised electrons → conducts, malleable
Pakistan Example
Copper Wires and Salt — Bonding in Pakistani Homes
Every copper wire in a Pakistani home uses metallic bonding — delocalised electrons flow freely as current. Table salt (NaCl) in every kitchen is ionic — it dissolves in water and conducts electricity in solution, which is why salt water is dangerous with live wires. AKU-EB Chemistry regularly tests bonding type from properties given.