SolutionsHistory
1. Atom
What does the word atom mean? Who proposed the idea and what was it based on?
A-tomos means "indivisible". It was proposed by Leucippus and his disciple Democritus, in ancient Greece, by philosophical reasoning and without any experimental evidence.
2. Thomson
Why are cathode rays deflected towards the positive plate? What did Thomson measure?
Because they are made of negatively charged particles: electrons. Thomson measured the charge-to-mass ratio of the electron (1897).
3. Rutherford
What did Rutherford conclude when he saw some alpha particles bounce back from the gold foil?
That the atom is almost entirely empty space, with a very small, positively charged central nucleus that deflects or bounces back the few alpha particles that pass close to it.