Short history of the concept 'atom'
There are many websites about atoms.
- The word 'atom' appeared for the first time in the Old Greek Period, 400 befor Christ, when the phylosopher Democritos applied the concept.
"a-tomos = not cutable" (cannot be cut into smaller pieces)
He invented in his mind the smallest particles ever of matter.
Imagine: one cristal of sugar that you try to cut with a razor blade into the finest pieces.
At a certain moment this is not longer possible. The sugar part can no longer been cut. It cannot longer be divided.
That this particle would turn out to be so small as what we now call 'atomd', that he certainly did not imagine.
The properties of a substance, according to Democritos, depend directly on the shape of that smallist particle: itching substances must have atoms with a needle shape, because they prick. And sugar atoms must have a nice round shape; they feel/taste well on the tongue.
Every substance, in the view of Democritos, has its own atoms. Well, there are enormously many substances, so there must be many different atoms.
We have now other thoughts about that.
John Dalton (1803) went back to that concept of 'atom' as the elementary particles, building stones of all substances. But according to Dalton the number of different atoms is limited. Different substances are constructed by composing with different atoms (making molecules).
- Thomson (1897) discovered the electron in the atom.
- Rutherford (1871) discovered the nucleus and the composition of it.
- Today we know lots and lots more about particles of atoms, like quarqs and the neutrino.