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400
Democritus Atomic Theory (400 b.c.)
Democritus found that atoms are not all the same, they are eternal, and always moving. He made a theory on this to explain why and how atoms were so small, and what they were about. -
John Daltons Atomic Model
Dalton found the atomic weight, and chemical symbols, and discovered proportions of elements in compounds. -
Plum Pudding Atomic Model
J.J. Thomson discovered electrons, and then said the atom was a sphere of positive electricity, with negative particles throughout it. -
Rutherfords Atomic Model
Rutherford discovered the atomic nucleus. He used a thin foil made of gold metal to find positive and negative charges in an atom. -
Niels Bohr's Atomic Model
Bohr's atomic model shows a positively charged nucleus surrounded by electrons. -
Niels Bohr
He figured out the structure of the atom, and their radiations, and started the basis of quantum theory. -
Electron Cloud Model
Erwin Schrödinger and Werner Heisenberg discovered the electron cloud model. They said an atom consists of a dense nucleus and many proton and neutrons and is surrounded by electrons, but they all have different energy levels, and different charges. -
James Chadwick
He discovered the neutron when alpha waves bounced off of them and they showed no charge. -
Planetary or Solar System Models
Rutherford said the atom is mostly empty space with a nucleus that has a positive charge surrounded by negative electrons. Then Bohr said they circulate the atom. -
Aristotle Atomic Theory (384 b.c.)
Aristotle discovered that matter is made up of atoms, and that it cant be created or destroyed. He also found that there are four elements, from which he came up with the theory of motion.
