1. A Brief History of the Modern Atomic Model 1803 - 1950’s Pgs 102-114, Chemistry Matter and Change

2. John Dalton in 1803 Redeveloped Democritus' atomic theory that matter can be crushed into smaller pieces. The smallest piece of matter that cannot be crushed any farther was called the atom. He measured the amount of different elements that form with each other during chemical reactions.

3. Sir William Crookes – late 1800’s Connected atoms to electricity Developed cathode ray tubes and proved through experimentation the presence of a charged particle. - +

4. JJ Thompson – 1890’s Used cathode ray tubes to determine that atoms were made up of smaller particles with an electric charge (electron). JJ Thompson earned a Nobel Prize in 1906 for his revolutionary work. Proved Dalton’s assumption to be incomplete. His discovery became known as the plum pudding model.

5. Plum Pudding Model

6. Ernest Rutherford – 1911 Shot positive charges through a thin piece of gold and determined that most positive charges did not bounce back, but went through the gold. Determined that the atom is mostly empty space

7. Rutherford’s Experiment

8. Niels Bohr - 1913 Worked in Rutherford’s Lab Calculated the radius of each electron orbit for hydrogen and developed theory that light is produced when electrons are excited to another electron orbit (energy level) and then fall to their original position His work lays the groundwork for all other scientists that studied the energy of electrons.

9. Bohr Model

10. Quantum Mechanical Model - 1920’s - present Electrons do not orbit around the nucleus, but we can determine the probability that they are in a given space (around the nucleus). We cannot see atoms, but math shows this is the “best” model we have.

11. History of Atom History Book Project (20 pts) You must have one page for each development of the atomic model. On each page you must include: 1.An image or drawing that shows an important part 2.A sentence or two about the person who developed the atomic model 3.A sentence or two about why the atomic model was so “ground breaking.”