Democritus - 429 BCFirst person to think of the atom.
Thought atom was a sphere.
Aristotle - 400 BCHe thought that everything was made up of one of the four elements.
He did not believe in atoms.
Isaac NewtonHe believed that there were tiny pieces of mass "swimming" around everywhere.
John DaltonHe discovered Atomic Theory.
All matter is composed of atoms.
Atoms can be made and destroyed.
All atoms of the same element look the same.
Different atoms have different types of atoms.
Chemical reactions occur when atoms are rearranged.
Compounds are formed from atoms of different elements.
Henri BecquerelHe helped discover radioactivity.
J.J. ThomsonHe discovered electrons.
Made the "plum pudding" model.
Robert MillikanHe found the measure of the charge of an electron.
He found the mass of an electron.
Ernest RutherfordFound that an atom has a central positive nucleus surrounded by negative orbiting electrons.
Neils BohrHe thought that the atom had a small positively charged nucleus with negatively charged surrounding electrons orbiting it.
Francis AstonHe discovered 212 natural isotopes
He invented the mass spectrometer.
Erwin SchrondingerFound that the atom has clouds of energy and that it has a nucleus.
He made an equation to find out where the electron would be in an atom.
He proved the Bohr model incorrect.
James ChadwickDiscovered that neutrons are congruent to protons in weight.
Discovered the neutron.