1. Rutherford and Bohr Rutherford – Structure of the Atom
Remember the existing model of atom is the Plum pudding model from JJ Thomson
Have electrons and everything else is postive
So Rutherford does experiment that is outlined on the next slide

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3. Sir Rutherford’s Experiment
Shot alpha (+) particles at gold leaf (small # of atoms thick)
Around gold leaf placed chemical coated material that detected presence
of alpha particles by showing a green glow
The experiment was run for days and his graduate student kept track of
the location and number of green glows.

4. Sir Rutherford’s Gold Foil Experiment Results
Angle of deflection (degrees)
# of deflection
0-5 (straight thru)
8,289,000 10
502,570 15
120,570 30
7,800 45
1,435 60
477 75
211
>105 (bounced back)
198
What does lab data tell use:
1) 0-5degree shows that 8 out of 9 particles went right thru.
Result – atom is mostly empty space
2) >105 degree shows that there must something in atom very massive
(i.e. high mass). Result – small volume massive center
10-75degree mean that the particle are deflected from their straight
path. Result – Since particle is + charge must be going
by a postive charge

5. Sir Rutherford’s Gold Foil Experiment
So what does this tell us.
Rutherford discovered in the atom: 1) A small volume (compared to the volume
atom)
2) Massive (high mass area)
3) Positively charge
Rutherford called it the “nucleus”.
His experiment did not discover anything about the electrons.
He postulated that the electrons are moving around the nucleus like the planets
around the sun. THIS IS WRONG.
We call it RUTHERFORD SHORTCOMING.
WHY IS IT WRONG????

6. Rutherford’s shortcoming
He says that the electrons (a negative particle) will move around the nucleus (positive particle) in a specific path without energy change.
Problem: It breaks the laws of physics. Without getting too physic specific,
this can’t happen without the electron doing one or two things:
1) spiraling into the nucleus due to coulombic force attraction
2) you constantly giving energy to the electron to counterbalance
the coulombic force attraction so it stays at specific distance
from nucleus.
SO WHAT DID RUTHERFORD’S GOLD LEAF EXPT SHOW:
Answer: Structure of the atom, small massive “+” charge center called nucleus
His explanation of electron movement IS WRONG