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442 BCE
Democritus
Atoms are the building block for everything. Atoms can't be broken down any father than what they are now. -
350 BCE
Aristotle
All materials on Earth are not made of atoms, but of the 4 elements Earth, Fire, Water, and Air. -
Evangelista Torricelli
Discovered that air has weight and can push down a column of mercury. -
Antoine Lavoisier
stated that all mater couldn't be created or destroyed. -
John Dalton
Father of the atomic theory. All matter is composed of small particles called atoms,atoms of the same element have an identical size,shape and mass, atoms of different elements differ in size and mass, atoms of different elements combine in simple whole-number ratio's to form chemical compounds, and atoms cannot be subdivided, created, or destroyed. -
JJ Thomson
Discovered the electron by experimenting with the cathode ray tube. Created the pudding model. -
Robert Millikan
His oil drip experiment helped qualify the charge of an electron. -
Ernest Rutherford
Gold foil experiment demonstrated that the atom has a tiny, heavy nucleus. -
Niels Bhor
Energy is transferred only in certain well defined quantities. Electrons move around the nucleus in prescribed orbits, the negatively charged electrons travel around the positively charged nucleus. -
Louis DeBroglie
Predicted the wave nature of electrons. -
Erwin Schrodinger
used mathematical equations to find exact position of electron. -
James Chadwick
Discovered neutrons in the atom.