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Democritus
(BC)
He was the first to suggest the existence of atoms. -
Isaac Newton
He was an English mathematician.
He thought the atom was a "dot."
He thought Democritus was right about the atom. -
John Dalton
"Dalton's Atomic Theory"
1. All elements are composed of indivisible atoms.
2. Atoms of the same element are identical; atoms of different elements are different.
3. Atoms form compounds.
4. Atoms are rearranged, not created or destroyed, in a chemical reaction. -
Dmitri Mendeleev
He created the first periodic table.
The elements were organized by atomic weight. -
J.J. Thomson
He discovered the electron.
He used the "Plum Pudding Model." -
Ernest Rutherford
"Gold Foil Experiment"
The atom has a positive nuclues (protons).
Everything else in the atom is mostly empty, except the electrons, which orbit the core, or the nucleus. The nucleus makes up a very small part of the atom's volume. -
Max Planck
He showed that when you vibrate an atom enough, you can measure the energy. This is called quanta. -
Niels Bohr
He said that electrons orbiting the nucleus are on different energy levels. -
Albert Einstein
Atomic power: e=mc^2 -
Millikan
Oil Drop Experiment
He found the mass and charge of an electron.
He said the mass of an electron is 1/2000 that of a proton. -
Chadwick
He discovered the neutron.
