Giant covalent compounds (Macromolecules)
Macromolecules are giant covalent structures.
When atoms share pairs of electrons, they form strong covalent bonds. Macromolecules contain a lot of non-metal atoms, each joined to adjacent atoms by covalent bonds. Their atoms are arranged into giant lattices or networks.
Macromolecules have very high melting points, because a lot of strong covalent bonds must be broken.
Examples of macromolecules
Diamond, graphite and silica.
Structure of Macromolecules
Properties of giant covalent structures (Macromolecules)
Very high melting points
Substances with giant covalent structures have very high melting points, because a lot of strong covalent bonds must be broken. For example graphite has a melting point of more than 3,600ºC.
Macromolecules show variable conductivity. Diamond does not conduct electricity. Graphite conducts electricity because it contains free electrons. Silicon is semi-conductive, i.e. midway between non-conductive and conductive. The fact that it is a semi-conductor makes it useful in the electronics industry as most transistors are made of silica.