The Atomic Theory, introduced on a scientific basis by John
Dalton in 1806, revolutionized the way that humans thought about
matter in the universe.  It created a view of matter that was
elegant in its simplicity - all of the changes that take place
around us every day are simply due to rearrangements of nature's
fundamental building blocks, which we call atoms    There are a
limited number of different types of atoms (92 that occur in
nature), from which all of the millions of substances around us
are "built."  Each different type of atom (called an element) is
represented by a unique symbol.  One interesting fact is that
John Dalton himself (who was a bit idiosyncratic) wished to use
pictorial symbols for the elements, using pictures that he
thought represented some aspect of the chemical or physical
behavior of that particular element.  He was overruled in favor
of using various combinations of letters as the elemental
symbols (less creative perhaps, but a lot faster to write and
more consistent from one p