AQA C2 (Old spec

Those in bold are higher tier

Molecules

1) Substances that consist of simple molecules are gases, liquids or solids that have relatively low melting points and boiling points.

2) Substances that consist of simple molecules have only weak forces between the molecules (intermolecular forces). It is these intermolecular forces that are overcome, not the covalent bonds, when the substance melts or boils.

3) Substances that consist of simple molecules do not conduct electricity because the molecules do not have and overall electrical charge.

Ionic Compounds

1) Ionic compounds have regular structures (giant ionic lattices) in which there are stong electrostatic forces in all directions between oppositely charged ions. These compounds have high melting points and high boiling points because of the large amounts of energy needed to break the many strong bonds.

2) When melted or dissolved in water, ionic compounds conduct electricity because the ions are free to move and carry the current.

Covalent Structures

1) Atoms that share electrons can also form giant structures of macromolecules. Diamond and graphite (forms of carbon) and silicon dioxide (silica) are examples of giant covalent structures (lattices) of atoms. All the atoms in these structures are linked to other atoms by strong covalent bonds and so they have high melting points.

2) I diamond, each carbon atom forms four covalent bonds with

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