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Democritus was the first person recorded in history to say that there is a limit to matter. After dividing something at one point it finishes. He called this atomos that means undivisable. After that for centuries nobody agreed or experimented with him because of Aristotle disagreeing and influencing others.
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To Dalton :
All matter is made of atoms. Atoms are indivisible and indestructible.
All atoms of given element are identical in mass and properties.
Compounds are formed by a combination of two or more different kinds of atoms.
A chemical reaction is a rearrangement of atoms.
Atoms can be neither created nor destroyed. -
Dalton died in Manchester, England at the age of 77.
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Joseph John Thomson is born in Manchester, England.
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Ernest Rutherford was born in Brightwater, New Zealand.
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Niels Bohr was born in Copenhagen, Denmark
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A new atomic theory was out. Thomson said that it is not divisible, but is made up of smaller pieces: protons and electrons.
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"Ernest Rutherford publishes his atomic theory describing the atom as having a central positive nucleus surrounded by negative orbiting electrons. This model suggested that most of the mass of the atom was contained in the small nucleus, and that the rest of the atom was mostly empty space. Rutherford came to this conclusion following the results of his famous gold foil experiment." (http://www.rsc.org/chemsoc/timeline/pages/1911.html)
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He improved the ideas of Rutherford:
Electrons orbit the nucleus without losing energy;
Electons could move only in fixed orbits of specific energies.
Electrons with low energy would orbit closer to the nucleus while electrons with high energy orbit further from the nucleus. -
Like light, electrons could be waves and particles. This is how colors are produced by electrons.
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James Chadwick identified the neutron. He said it had no charge, but it did have mass.
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Rutherford died in Cambridge, UK at the age of 66
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At the age of 83 Thomson died in Cambridge, England.
