Ionic substances form giant ionic lattices [lattice: A lattice is a regular grid-like arrangement of atoms in a material. ] containing oppositely charged ions. They have high melting and boiling points, and conduct [conduct: To allow electricity, heat or other energy forms to pass through. ] electricity when melted or dissolved in water.

Simple molecular substances consist of molecules [molecules: a collection of two or more atoms held together by chemical bonds. The fundamental unit of compounds ] in which the atoms are joined by strong covalent bonds [covalent bonds: A covalent bond between atoms forms when atoms share electrons to achieve a full outer shell of electrons. ]. Their molecules are held together by weak forces, so these substances have low melting and boiling points. They do not conduct electricity.

Giant covalent structures contain many atoms joined together by covalent bonds to form a giant lattice. They have high melting and boiling points. Graphite and diamond have different properties because they have different structures. Graphite conducts heat and electricity well because it also has free electrons.

Nanoparticles are 1-100 nm in size, typically the size of small molecules - far too small to see with a microscope. They have remarkable properties that are different to the same substance in bulk form.

Metals form giant structures containing free electrons [electrons: Sub-atomic particles, with a negative charge and a negligible mass relative to protons and neutrons. ], making them good conductors of heat and electricity.