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John Dalton explained in a publishing that each element is made up of atoms, which all have different masses. Dalton imagined atoms looking like small, solid balls.
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J.J. Thomson proposed a model that suggested that an atom is a sphere that is positively charged with electrons embedded in it. This model looked like a berry muffin.
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Hantaro Nagaoka proposed that the atom had a large sphere in the center that was positively charged. His model resembled the electrons revolving around just like planets in space.
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Ernest Rutherfurd found that an atom is mostly full of empty space. He thought that it was a small, positively charged nucleus that has electrons orbititing randomly.
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Niels Bohr came up with the theory that electrons moved in specific layers. He thought that atoms absorb energy when they move from one to another.
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James Chadwick discovered the neutron. The neutron is a particle with the same mass as a proton without a charge. This explains why atoms were heavier than the mass of the protons and electrons combined.
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The current model came from the work of scientists from the 1920's to the present. This model shows the electrons forming a negatively charged cloud around the nucleus. You can never tell where an electron is at a specific time.
