I've got a question for you guys. Do you think I can fit this length of polystyrene into this jar? Yes. No. No? Yeah? I like that – you lot have got some faith in me! Excellent. Right, this is what we ...

Everything we can see and touch, and quite a lot that we can’t as well, is made of tiny particles called atoms. Some substances, like particles of this iron, contain only one kind of atom. Iron is an ...