1. Ernest B. Rutherford

2. Previous Model
The previous model of the atom was the plum pudding model, where the atom is a mass of positive matter, with ’plums’ of negative electrons scattered throughout.
If Thompson’s model is correct, the mass of the atom should be evenly spread throughout. Rutherford was going to perform an experiment to test this theory.

3. Experimental Design
Testing to see if the plum pudding model was accurate, Rutherford conducted an experiment where a beam of positive alpha particles(helium nuclei) were aimed at a very high velocity to see if they would pass through a gold sheet (a zinc sheet was behind it to catch the particles).
While doing this, most particles passed through as expected, but few either were deflected backwards or were diverted back at dramatic angles.

4. Experiment

5. Conclusions From this experiment Rutherford was able to conclude:
The atom is 99.99% empty space.
That the atom contains a nucleus that is positively charged and contains most of the mass of the atom.
The nucleus is 10,000 times smaller than the atom.

6. Reason for New Model
The atoms either went right through, bounced back, or diverted at dramatic angles.
If the plum pudding model were correct, the particles would have had their courses only slightly changed by the charge within the atoms.
This meant that Thompson’s plum pudding model wasn’t correct, since the only way the alpha particles could be deflected backwards was if most of the mass of the atom was concentrated in the nucleus. This led to Rutherford proposing a new model of the atom.

7. New Atomic Model
Rutherford’s new model had a dense, positively charged nucleus containing all of the protons(positively charged atoms) in the center, with negatively charged electrons orbiting around it. Similar to the planets revolving around the sun.

8. Interesting Information
He was knighted in 1914.
The element 'rutherfordium' was named in his honor.
He is known as the father of nuclear physics.

9. Links Used
model.html