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400
Democritus
Around 400 B.C. First model of an atom. He was also the first to think about an atom. His model of an atom was like a circle. -
500
Leucippus
Around 500 B.C. He thought everything was made up of something. -
550
Aristostle
Around 500 B.C. He opposed Democritus' theory. He believed there were only four elements that were fire, water, air, and earth. -
Isaac Newton
Newton came up with the three laws of motion but it did not involve the atom. -
John Dalton
John Dalton had came up with "Dalton's Atomic Theory".
1. All matter is made of atoms.They are indivisable.
2.All atoms of the same element are the same. Atoms of different elements are different.
3. Atoms combine to make compounds.
4. Atoms are rearranged- not created or destroyed- in a chemical reaction. -
J.J. Thompson
He discovered electrons after other thought there were particles that made up an atom. He used the cathode ray tube to discover electron. He also made up the plum pudding model. -
Ernest Rutherford
He found that atoms have positive charges in a small but dense nucleus. He did this through the "gold foil experiment". -
Neils Bohr
He discovered that electrons traveled on rings or energy levels. The more rings, the higher the energy levels. They can move from ring to ring, but it takes more energy. -
Schroedinger
He described a cloud like region where an electron is likely to be found. -
John Chadwick
He discovered the neutron because of an odd differences in mass.
