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400 BCE
Democritus
Democritus was born in 460 BC and dies in 370 BC. He was the man to develop the name "atomos". He adopted the atomic theory-created by his mentor around 465 BC- which says that everything is made up of atoms and the empty space in which they move. He created the atomic model in 400BC. -
John Dalton
Through experiments with gases, Dalton discovered many things. First of all, he discovered that atoms make up matter and they cannot be created or destroyed. All atoms of an element are identical and atoms of different elements have different weights and properties. Finally, he discovered that atoms of different elements combine to make compounds, -
JJ Thompson
He experimented with a cathode ray tube. Doing so, he discovered the electrons. With his information, Thompson created the "plum pudding" model, where the atom is a large positively charged ball filled with negatively charged electrons- the plums in the pudding. -
Ernest Rutherford
He conducted the Geiger-Marsden experiment, also own as the Gold Foil experiment.
The Rutherford Gold Foil experiment shot alpha particles at a thin sheet of gold. It was found that a small percentage of the particles bounced back, while most passed through the sheet. This caused Rutherford to conclude that the mass of an atom was concentrated at its center. He stated that the atom has a tiny, heavy nucleus with orbiting electrons. -
Niels Bohr
Bohr discovered a major flaw in Rutherford's model; the orbits of the electrons were unstable. Niels created the Bogr Model, showing that electrons actually revolve in stable orbits around the nucleus. He also discovered that they can "jump" from one orbit to another depending on an increase/decrease in their energy levels.
