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370 BCE
Democritus
Democritus first came up up with the atomic theory. It stated:
Everything is composed of tiny invisible atoms.
Between atoms there is empty space.
Atoms cannot be destroyed.
Atoms will always stay in motion.
There are an infinite number of atoms, and range in many psychical properties.
Democritus believed that the atoms were solid and round, and interacted mechanically with each other. -
John Dalton
John Dalton added to Democritus's theory, and added new principles: All matter is made of atoms
Atoms cannot be broken down into smaller parts
Atoms of an element are the same, and the atoms of another element are different. His model was similar to Democritus's, he believed them to be small, indivisible spheres. He was not aware of the other parts in the atom. -
J.J Thomson
Thomson discovered that atoms held the electron which were in positively charged matter. His discovery proved that atoms were composed of smaller parts.
Thomson proposed the "Plum Pudding Model" where the model demonstrated the electrons (plums) of the atom surrounded by positively charged "pudding" to balances their negative charges. -
Neils Bohr
Bohr added to Rutherford's model, and used his experimental evidence to support the idea that electrons were found in the atom.
The Bohr model depicted the atom as a small, positively charged nucleus with electrons that surrounded it. -
Ernest Rutherford
Rutherford made the discovery of the nucleus, and concluded that it was essential to the atom. This even further proved that all atoms were composed of smaller parts.
His model described particles beamed through gold foil, and detecting the parts as flashes of light.
