Chemical Bonding: Ionic, Covalent, Metallic in Plain English
May 9, 2026 · 5 min · chemical bonding · ionic vs covalent · chemistry help
Three bond types cover most of GCSE, IGCSE, A Level, and AP Chemistry. Each one is just a different answer to the same question: what do atoms do with their outer electrons?
Ionic bonding
One atom gives an electron to another. The donor becomes a positive ion (cation). The receiver becomes a negative ion (anion). They stick together by electrostatic attraction.
- Happens between metals and non-metals
- Big electronegativity difference (>1.7 on the Pauling scale)
- Forms crystals with high melting points
- Conducts electricity when molten or dissolved (ions free to move)
Examples: NaCl, MgO, CaCl₂.
Covalent bonding
Two atoms share electrons.
- Happens between non-metals
- Small electronegativity difference (<1.7)
- Forms either molecules (H₂O, CO₂) or giant covalent structures (diamond, SiO₂)
- Molecules: low melting points, don't conduct electricity
- Giant covalent: very high melting points, mostly don't conduct (graphite is the exception)
Metallic bonding
Metal atoms pool their outer electrons into a "sea". The positive ions sit in the sea.
- Happens between metals
- Conducts electricity (delocalised electrons)
- Malleable and ductile (ions can slide past each other)
- Usually high melting points
How to predict which bond
- Look at the elements
- Metal + non-metal → ionic
- Non-metal + non-metal → covalent
- Metal + metal → metallic
Then use the Pauling scale electronegativity difference to refine.
Common pitfalls
- Calling H₂O "ionic" because it's polar (it's covalent — they share electrons unequally, but they share)
- Forgetting that ionic compounds need both a cation and an anion
- Confusing intermolecular forces (between molecules) with intramolecular bonds (within a molecule)