Mrs Roberts: What do you think you're made of? Mr Spellman: Big question. Grit, determination, hard-working, handsome, charming, funny. Mrs Roberts: Well, I guess. But you're actually made of atoms.

For example, the formula H 2 O shows that a water molecule contains two hydrogen atoms and one oxygen atom.

THIS is a set of cardboard pieces printed with the symbols of elements and common radicles, and graduated in size according to predominant valency; positive radicles are blue, negative are pink. The ...