History of Atomic Theory

List the three pieces of evidence for Dalton’s atomic theory.

1) Law of Constant Mass

2) Law of Definite Proportions

3) Law of Multiple Proportions

What does the Billiard Ball Model look like?

Just a circle

Atoms combine in whole _______________ to form components.

Number ratios

What is the piece of evidence for Thomson’s model? How did this work?

Cathode ray tube

• Beam moved pinwheel so it contains matter

• Beam deflects to positively-charged plate, so there are negative particles

What is Thomson’s model? What did it look like and how did it work?

• Plum Pudding Model (or Chocolate Chip Cookie Model)

• Looked like circle contains negatively-charged ions

• Because of deflection of particles, he determined that they are smaller than an atom

What was the piece of evidence for the Rutherford model? How did it work?

• The Gold Foil Experiment

• Most α particles shot straight through the gold foil…most of the atom is very low density

What was another one of Rutherford’s models? Describe a diagram of it.

• Nuclear/Planetary Model

• Positively-charged molecule in center with electrons surrounding it