Chemistry 06202.5 Simple molecules and covalent bonds
3D molecule viewer
Rotate common IGCSE molecules in three dimensions and count the shared electron pairs in each bond.
- Covalent bonding
- Molecular shape
- Shared electron pairs
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Predict
Methane is tetrahedral rather than flat. Why?
Experiment
- 1Compare methane and ammonia. Ammonia has one fewer bond — what happens to the shape?
- 2Look at carbon dioxide and count the rods on each side of the carbon.
- 3Find the C=C double bond in ethene, the bond that makes it unsaturated.
Explain
A covalent bond is a shared pair of electrons. Sharing lets both atoms reach a full outer shell without transferring electrons.
The shape follows from repulsion between electron pairs. Four bonding pairs give a tetrahedron; three bonding pairs plus a lone pair give a pyramid; two bonding regions give a linear molecule.
Boiling a simple molecular substance breaks only the weak forces between molecules, not the strong covalent bonds inside them — which is why methane boils at such a low temperature.