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460 BCE
Democritus
According to Democritus atomic theory, the universe and all matter obey the following principals. Everything is composed of atoms, all atoms are Indestructible -
384 BCE
Aristole
He believed everything was made up of one of the 5 elements. Air, Water, Fire, Earth, and Aether -
Dalton
his Atomic theory proposes that all matter was composed of Atoms. They were indivisible and indestructible building blocks. Different elements had Atoms of different sizes and mass -
Milikan
His oil drop experiment helped to quantify the charge of an electron. this helped a lot towards the understanding of the structure of the Atom and the Atomic Theory. -
Thomson
He discovered the electron when experimenting with a Crookes tube. Thomson realized that the accepted Atomic model of the Atom did not account for negative and positive charged particles. -
Rutherford
He overturned Thomson's Atomic Theory in 1911 with his Au foil experiment. He demonstrated that the Atom has a tiny and heavy Nucleus -
Bohr
In 1913 Bohr proposed a theory for the Hydrogen Atom based on the Quantum Theory that energy is transferred only in certain well defined quantities. -
Schrodinger
He took Bohr Atom structure one step further. He used mathematical equations to describe the likely hood of finding an electron in a certain position. -
Chadwick
He bombarded Beryllium atoms with Alpha particles. He produced an unknown radiation. He interpenetrated the radiation as being composed as particles with a neutral electrical charge.