Making light of metals

	Published by Australian Academy of Science
Making light of metals Box 1 \| The magic of metals

Many of the 90 or so naturally-occurring chemical elements are metals; indeed the remaining couple of dozen are known collectively as non-metals. We can pick a metal by looking at its properties. Metals have a lot of properties in common:

All but one of the common metals (the exception being mercury) are solids at room temperature. Non-metals can be solids, liquids or gases.
Metals are either naturally shiny or can be made to show a lustre.
Metals are ductile; that is, they can be drawn out to form wires.
Metals are malleable; that is, they can be hammered or rolled into thin sheets (think of gold leaf or aluminium foil). They can also be bent without breaking.
Metals are generally good conductors of both heat and electricity. Of the non-metal elements, only carbon conducts electricity well.

Many of these properties come from the distinctive way that the atoms of metals are held together (or bonded). Metallic bonding is the result of the outer electrons of the metal atoms escaping and drifting freely in a sort of ’electron sea’ in which the atoms are embedded. The sharing of free electrons forms the bond (or force of attraction) of the atoms, holding them in a crystal lattice. The more electrons there are on the loose, the stronger the metal and, in general, the higher its melting point.

It is these wandering electrons that conduct electricity and heat so well.

Metals can be hammered and drawn out into wires because the metal atoms can slide past one another without breaking the bonds. The free electrons can rearrange with the new shape, holding the atoms together.