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Democritus
One of the founders of the ancient atomic theory. He believed all matter consisted of extremely small particles that could not be divided. -
John Dalton
Dalton said that all matter is made up of individual particles called atoms which can't be divided. Each compound contains atoms of more than one element. Atoms of different elements all combine the same. -
J.J. Thomson
Thomson's experiment provided the first evidence that atoms are made of even smaller particles. In hs experiment, when a current is turned on, a disk becomes negatively charged while another disk becomes positive. A beam appears in the tube between the disks. Tomson discovered that particles came from inside atoms. -
Hanataro Nagaoka
He made an incorrect planetary model of the atom. He assumed atoms were large, positively charged spheres surrouned my negatively charged electrons. He thought the atomic spectra should be direcly related to the electrons orbit frequency. Although he was mostly wrong, it led to the discovery of atoms' rings. -
Ernest Rutherford
He studied the absorbtion of radiation by using sheets of gold foil. He said that most of the atom was contained in the nucleas and the rest was mostly empty space. He shot radiation particles through sheets of metal and deflected them using screens. Some were deflected and some shot straight through. -
Niels Bohr
He said electrons travel in stationary orbits defined by their momentum. That led him to the calculations of possible energy levels. It is based on quantum mechanics. The negatively charged electrons orbit the positive nucleous. -
Werner Heisenberg & Erwin Schrodinger
They said an electon cloud is an atom with a nucleous in th center. Many rings go around it but not in a specific order. -
James Chadwick
He discovered the nuetrons in an atom. Those are the neutrally charged atoms. Niether negative nor positive. He also suggested that new radiation consisted of uncharge particles of the mass of the proton.
