1. The Parts of an Atom

2. J.J. Thomson
He experimented with cathode ray tubes

3. He passed electricity through the tube and discovered the first subatomic particle – the electron
He developed the plum pudding model of an atom

4. Plum Pudding Model

5. Robert Millikan He determined that the electron has a negative charge
He determined the mass of the electron

6. Ernest Rutherford
He proved the plum pudding model was incorrect with the gold foil experiment

7. Gold Foil Experiment
positive alpha
particles

9. He discovered the nucleus of the atom!
The nucleus is the dense, positively charged center of the atom
He came up with the Nuclear Atomic Model

10. Nuclear Atomic Model
Nucleus
Electron

11. Years later, Rutherford discovered the proton
proton = a positively charged particle inside the nucleus +
nucleus
proton

12. James Chadwick worked with Rutherford
discovered the neutron – a particle in the nucleus with the SAME MASS as a proton, but with NO charge (it’s neutral)!

13. Modern Atomic Structure
spherically shaped
most of atom’s mass is in the nucleus (99.7%)
nucleus surrounded by negative electrons

14. Atoms have no charge (they are electrically neutral) because the number of protons is equal to the number of electrons
3 protons (+)
3 electrons (-) + -

15. *Electron has the least mass
particle
symbol
location
charge
mass (g)
relative
mass
electron
e –
in space
around
nucleus –
9.11 x 10 – 28
_1__
1840
proton p+
inside +
1.673 x 10 – 24 1
neutron n0 no
*Electron has the least mass

16. You Made It!!!