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John Dalton concluded that each element is made of atoms that are all alike. Dalton imagined atoms as tiny, solid balls.
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British scientist J.J. Thomson purposed the new model suggesting thhat an atom is a positively charged sphere with electrons embedded in it,.
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British physicist Ernest Rutherford discovered that an atom is mostly empty space and that electrons orbit around a small, positivly charged nucleus.
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Danish physicist Niels Bohr proposed a model that showed electrons traveling in specific layers or shells rather than randomly. He said that atoms absorb or give off energy when the electrons move from one shell to another.
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British physicist James Chadwick discovered the neutron. The neutron explained why atoms were heavier than the total mass of their protons and electrons.
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The current model shows that electrons form a negativly charged cloud around the nucleus.It is impossible to determine exactly where an electron is at a given time.
