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John Dalton
Common substances always broke down into the same elements with the same proportions. Atoms cannot be created nor destroyed. His model called the billiard ball model showed that each chemical element is composed of atoms of a single, unique type. -
JJ Thomson
His experiment involved cathode ray tubes that showed that all atoms contain tiny negatively charged subatomic particles or electrons. His model was the "plum pudding" model, a model that showed positive and negative charged particles inside an atom. -
Ernest Rutherford
He shot alpha particles at a piece of gold foil that was 3 atoms thick. He discovered that the alpha particles were going through the gold foil and some would be bounced back off the nucleus or some were bent by the electrons. His model depicts an atom with a nucleus with electrons scattered around it. Observation 1, most particles travel through the foil undeflected. 2, Some alpha particles are deflected by small angles. 3, Occasionally an alpha particle travels back from the foil. -
Niels Bohr
Bohr was the first to discover that electrons travel in separate orbits around the nucleus and that the number of electrons in the outer orbit determines the properties of an element. His model depicts the way in which electrons travel around the nucleus. -
James Chadwick
He discovered the Nuclei have neutrons which have no charge and are neutral. Isotopes of the same element have the same number of protons and electrons but differ in the number of neutrons found in the nucleus.