The rich variety of our world is matched by the diverse properties of the chemical elements from which it is made.
|Gold| is a solid, |mercury| is a liquid and radon is a radioactive gas.
Place gold in water and it is completely unreactive, put |sodium@in@water| and it catches fire, potassium reacts even more violently and ignites in a lilac glow, while lithium just bubbles.
We need sodium and potassium in our diet and we may take lithium carbonate as a drug to counteract depression, but if we were to ingest mercury we would become mad as hatters.
Beneath this assorted diversity there are patterns which can be discerned, and order that can be brought from apparent chaos, as Mendeleev did over a hundred years ago.
Out of his ideas came the form of the periodic table that is the cornerstone of chemistry today.
