Chemical bonding: ionic, covalent and metallic
Atoms bond to reach stable, full outer shells, and they do it in three ways: transferring electrons (ionic), sharing them (covalent), or pooling them (metallic). Knowing which bonding a substance has lets you predict its melting point, conductivity and more.
Key facts
| Topic | Chemical Bonding & Structure |
| Ionic | metal + non-metal; electrons transferred |
| Covalent | non-metals; electrons shared |
| Metallic | metals; a 'sea' of electrons |
Ionic bonding
A metal gives electrons to a non-metal, forming positive and negative ions that attract in a giant lattice. Ionic compounds have high melting points, and they conduct electricity when molten or dissolved (the ions are free to move) but not when solid. You should understand these properties, though K324 does not require you to draw the lattice itself.
Covalent bonding
Non-metal atoms share pairs of electrons. This gives either small simple molecules (like water or carbon dioxide) with low melting points and no conductivity, or giant covalent structures (like silicon dioxide) with very high melting points. You should know the contrasting properties; drawing the structures of diamond and graphite is not required.
Metallic bonding
In a metal, the atoms release their outer electrons into a shared “sea” that holds the positive ions together. This explains why metals conduct electricity and heat, and why they are malleable — the layers slide while the electron sea keeps them bonded.
Bonding predicts properties
Exam questions often give a property (melting point, conductivity in different states) and ask you to deduce the bonding, or vice versa. Anchor your answer in the structure: free-moving charged particles mean conductivity; strong forces throughout a giant structure mean a high melting point.
Frequently asked questions
What are the three types of bonding?
Ionic (electrons transferred between a metal and non-metal), covalent (electrons shared between non-metals), and metallic (electrons pooled in a 'sea' around metal ions).
Why do ionic compounds conduct only when molten or dissolved?
Their ions are locked in place when solid, but become free to move — and so carry charge — when the compound is melted or dissolved.
Do I need to draw diamond and graphite structures?
No — K324 does not require drawing the diamond or graphite structures, or ionic lattices. You do need to explain their properties.
How does metallic bonding explain a metal's properties?
The shared 'sea' of electrons carries charge (conductivity) and lets layers of ions slide without breaking the bonding (malleability).
G3 Chemistry, made clear
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