Rutherford's scattering experiment

I spent the last 15 minutes trying to find up good material to write about and was going to write up about my easter holidays and how boring it is as I study for my tests looming around the corner, only to just scrap it and talk about something more fun.

So I am going to talk to you about Rutherford's scattering experiment, one of the most revolutionary experiments to have ever been conducted, proving the construction of the nucleus of an atom.

The hero himself, Ernest Rutherford

 

The Rutherford Scattering Experiment

Originally, the nucleus was theorized to be made out of electrons surrounded by a mass of positively charged matter. The negative charge was equal to the positive charge and thus was neutral. This was theorized by Joseph John Thomson in 1904.

In 1911, Ernest Rutherford wanted to test this theory by firing alpha particles at the gold atoms. He picked gold as it is very easy to spread thin and could therefore make it so that it is only a few centimeters thick. He then fired the alpha particles at the gold atoms, hoping to break them apart. What he was surprised to find however, was that the alpha particles didn't break apart the nucleus but scattered in all directions. Some even scattered back towards the source! Everyone was surprised at the results; this was similar to firing a machine-gun at a tissue paper and finding some of the bullets being sent back!

Rutherford then realized that this could be explained if the nucleus of the atom has a positive charge. This could explain the repulsion of the alpha particles in different directions.  

The Atomic Structure

When Rutherford sat down to do calculations, he calculated that the size of the nucleus was very small when compared to the size of the atom. If you imagine magnifying the size of the atom until it is about the size of a football stadium, inclusive of the football field and basement, the nucleus in the center would be about the size of a tennis ball placed in the center. 

A neutron and proton are about the same mass. The electron however, if much lighter, 1800 times lighter than the mass of the neutron or proton. 

After effects:

He published his works, which are no doubt still being conducted today just to try and prove him wrong (although I doubt that he ever will be wrong. But thus is science). Note that there is no way to ever prove he is correct, thus the atomic theory will always remain a "theory". However at the time he received one of the greatest awards that one can ever hope to win - The Nobel Prize for Chemistry. (I would have preferred Physics though)