Rutherford's Gold Foil Experiment

Ernest Rutherford and the atom

Rutherford's experiment

How did Rutherford's gold foil experiment differ from his expectations?

He expected ALL the rays to pass through - only some bounced back.

Explanation:

Since the previous atomic model (the Thomson model) argues that an atom is a sphere of positive charge with the negatively-charged electrons scattered like "raisins in a pudding", Rutherford and his students fully expected that an α particle will pass through the gold foil with just a slight deflection on the angles since the α

particle is weakly positively charged.

In the case of the experiment, some of the α

particles did not only deflect at very large angles, but some even bounced back straight to the origin!

The experiment proves a number of things:

•  that an atom mostly consists of empty space (because the most of the rays went straight through)

• that something very solid (nucleus) is inside every atom to make some of the rays "bounce back"

• that the nucleus is positively charged to make some of the rays be deflected at odd angles (repels as in a magnet)

• there must be other particles present in the nucleus which are similar to protons but with no overall charge and called the particle a "neutral doublet"

Conclusion of the experiment

Rutherford's experiment showed the existence of a nuclear atom - a small, positively-charged nucleus surrounded by empty space and then a layer of electrons to form the outside of the atom.