Evidence for the Structure of Atoms
Our current picture of the atom wasn't created all at once; it was built up and improved step by step based on experimental evidence and some extremely clever insights.
Some ancient Greek philosophers speculated that everything might be made of little chunks they called "atoms." The name comes from a Greek word meaning "uncuttable"; atoms were supposed to be unbreakable, the smallest possible units of anything.
This is the same John Dalton I mentioned in our discussion of atomic weight. As I said then, he and others had noticed that elements in chemical reactions combine in certain definite proportions; this, Dalton guessed, had to mean that the elements were made of tiny, unbreakable chunks that always stick together in the same ways--two hydrogen chunks plus an oxygen chunk always makes water, for example.
So Dalton's guess was right.
It was, and it wasn't. The scientific world soon accepted that atoms did exist...but were they really unbreakable?
To find out more about Thomson and his experiments, you can take a look at the following links: