1. Atomic Theory

2. J.J. Thomson called the negative particles electrons
determined the charge to mass ratio of an electron

3. Cathode Ray Tube

4. Cathode Ray Tube (CRT)
negative end is the cathode
positive end is the anode
A cathode ray is radiation streaming from a cathode to an anode in a CRT
it is a stream of particles
a magnet can deflect the ray
cathode ray particles have a negative charge

5. Conclusions about Cathode Rays
J.J. Thomson showed that electrons were emitted from the cathode of a cathode ray tube.
Atoms are not indivisible, but contain internal parts, one of which is the electron.

6. Ernest Rutherford (Born in New Zealand 1871-1937)
Tested Thomson’s theory of atomic structure with the “gold foil” experiment in

7. Ernest Rutherford
alpha particles have a +2 charge (twice that of an electron, but charge is positive) What R used!
beta particles are high
speed electrons
gamma ray are not
composed of particles

8. Rutherford Gold Foil Experiment (alpha scattering)
he determined that an atom’s positive charge and most of its mass was concentrated in the core (most of the atom is empty space)
he named the core “the nucleus”

9. Rutherford's Gold Foil Experiment
Rutherford and coworkers aimed a beam of alpha particles at a sheet of gold foil surrounded by a florescent screen.

10. Rutherford’s Experiment

11. Gold Foil Experiment
Bombarded thin gold foil with a beam of ‘alpha’ particles.
If the positive charge was evenly spread out, the beam should have easily passed through.

12. Rutherford
Expected
Found

13. Rutherford's Experiment
Most particles passed through with no deflection, while some were highly deflected
Rutherford concluded that most particles passed through because the atom is mostly empty space.

14. Rutherford’s Conclusions
All of the positive charge, and most of the mass of an atom are concentrated in a small core, called the nucleus.

15. Size of Nucleus Compared to the Atom is as a Ball Compares to a Football Field.

17. Niels Bohr
Discovered that electrons orbit in specific energy levels “rings”
Planetary Model

18. Schrodinger
Schrodinger found that electrons so not orbit like planets but instead are found somewhere within an electron “cloud” at any given time
Each cloud has a different shape and energy level (s, p, d, f)

19. The Neutron
Discovered in by James Chadwick (England ).

20. Neutrons
Neutrons have mass similar to protons.
No electrical charge.

21. The Discovery of the Neutron
Chadwick bombarded Beryllium with alpha particles.
Neutrons were emitted and in turn ejected protons from paraffin.

22. Discovery of the Neutron

23. Plum Pudding Model (Thomson)

26. Draw pictures of the changing model of the atom
J.J. Thompson’s “Plum Pudding” model
Rutherford’s discovery of the nucleus
Planetary model
Quantum model

27. Plum Pudding Model
Rutherford Model
Bohr Model
Quantum Model