-
400
Democritus
(BC) First to think about an atom -
400
Aristotle
(BC) Opposed Democritus's theory; four elements make up everything: Earth, air, water, and fire -
500
Leucippus
(BC) Everything is made up of something -
Isaac Newton
Three laws of motion <-- no atom -
John Dalton
"Dalton's Atomic Theory" (see link) -
JJ Thomson
Used cathode ray tube to discover electron; made the plum pudding model -
Ernest Rutherford
Atoms have positive charges in a small, but dense nucleus; "gold foil experiment" -
Niels Bohr
Electrons travel on rings (energy levels). The more rings the higher the energy level. They can move from ring to ring, but it takes energy. -
Schroedinger
Described a cloud-like region where an electron is likely to be found -
John Chadwick
Discovered the neutron -
Thales of Miletus
(BC) Noticed Static
