18 apr 1909 anni - Ernest Rutherford

Descrizione:

Summary: Discovered proton.

Experiment: The Gold Foil experiment:

How did it work?:
A beam of alpha particles( created by radium) were targeted at a very thin sheet of foil. A microscope was used to observe the particles as they flashed when they came into contact with the Zinc that they put around the gold foil. (See experiment set up below). Most of the particles passed straight through but a small percentage of the alpha particles were deflected significantly. In fact, approximately 1 in every 20'000 particles reflected straight back. Rutherford said that this was similar to the effect if " you fired a 15-inch shell into a piece of tissue paper and it bounced back and hit you."

What changes did this make to the atomic model? Why were they important?:
This, therefore, disproved J.J Thomson's plum pudding model as, if the charge and mass were evenly positioned in the atom as Thomson said, the alpha particles would have passed through with far more ease. Instead, Rutherford proposed that electrons were instead, nearly weightless and floated around in an orbit around a small, highly dense nucleus. Through further experimentation, he discovered that this contained protons. This is important because it helped to explain why atoms were not all negatively charged and opened up the possibility of more and more sub-atomic particles.

What was this model called?:
This model was simply named after Rutherford as being the Rutherford Model.

Pictures:
Top:Self Portrait
Mid: The Gold foil experiment
Bottom: The rutherford model

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