Key learning points

1. Typical atomic radii, and bond length, are in the order of 10⁻¹⁰m.
2. Non-metal elements and non-metal compounds form covalent structures.
3. Simple covalent substances have no free moving charge carriers so cannot conduct electricity (some giant covalent can).
4. Small molecules are usually gases or liquids with relatively low melting and boiling points.
5. Giant covalent structures have high melting/boiling points because strong covalent bonds need to be broken.

Keywords

• Molecule - a particle consisting of a fixed number of (two or more) non-metal atoms covalently bonded together

• Covalent bond - the strong electrostatic force of attraction between a shared pair of electrons and the nuclei of bonded atoms

• Intermolecular forces - the weak forces of attraction between molecules and molecular substances

• Giant covalent structure - a substance that has a large regular arrangement of atoms all joined together by covalent bonds

• Polymer - a long chain molecule formed by joining small molecules (monomers) together by covalent bonds

Common misconception