ATOMISM

2. ATOMISM • Theory by Democritus and Leucippus • Objects in the universe are composed of very small atoms • Indestructible building blocks • Not indestructible • Believed hidden substances in all physical objects consists of different arrangements of atoms.

3. FOUR ELEMENTS • Aristotle came up with the idea that there were four different types of atoms. They were earth, wind, fire , and water. • They did not have scientific experiments . It was more of a philosophy.

4. SOLID SPHERE MODEL • John Dalton viewed the atom as a small solid sphere. • Each element was composed of the same kind of atoms. • Each element was composed of different kinds of atoms. • Compounds are composed of atoms in specific ratios. • Chemical reactions are rearrangements of atoms (mass is conserved).

5. PLUM PUDDING MODEL • J.J. Thomson in the Cathode Ray Experiment concluded that the particles inside were all negatively charged. This led to the development of the Plum Pudding Model • The plum pudding model of the atom was proposed by J. J. Thomson , who discovered the electron in 1897. • Then later Thomson proposed the plum pudding model in 1904.

6. GOLD FOIL EXPERIMENT • Ernest Rutherford • EXPERIMENT: he fired alpha particles at a very thin gold foil. • Shocking result: rather than all the particle passing straight through the foil, many were scattered off at different angles, some came straight back. • Electrons orbited the empty space around the nucleus.