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450
Democritus (460 BC)
Democritus discovered atoms are the smallest bit of matter that cannot be broken down.
He had the theory of a substance reaching a point to where itcould no longer be broken up but he had no real evidence.
He thought the atom looked like a marble. -
450
Aristotle (384-322BC)
Aristotle didn't support Democritus's idea of atoms and instead believed matter can always be made smaller. -
Dalton
Dalton said atoms are made of tiny particles and can not be divided.He believed all theatoms in one element are the same but are different from other element's atoms. He supported the atomic theory and thought the atom still looked like a marble. -
Thomson
Thomson discovered atoms are made up of smaller negatively charged particles called elecrons. He experimented with cathode ray tubes that showed the different charged. He made the Plum Pudding model that showed negatively charged electrons stuck in a positively charged substance. -
Rutherford
Rutherford discovered atoms have a nucleus that holds a positive charge. He believed electons surrounded the nucleus and were equal in amount to the protons. He performed a gold foil experiment that proved an atom is largely empty space. He created the nuclear model. -
Bohr
Bohr discovered electrons orbit the nucleus in a fixed circular orbit and electrons with low energy orbited closer to the nucleus than those with more energy. He created the Bohr model. -
Heisenburg and Schrodinger
They discovered electrons don't spin in orbits they spin in spherical orbitals. Heisenburg discovered the Quantum Theory which stated you cannot know the exact position and velocity of an atom. Schrodinger createdthe mathematical model of an atom which showed waves that electrons traveled on.
