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In 1803 John Dalton developed a simple theory of composition of atoms of different weights. He also discovered that the atoms are spherical.
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J.J. Thompson conducted a ray experiment which let to further examination that lead to the world's first x-ray
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Marie Curie studied, chemical compounds. This lead to a radiation that did not depend on the compound.
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He discovered that cathode rays were negatively charged particles. He also described the atom to be in the shape of a ball of positive charge containing lots of Electrons.
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Ernest Rutherford used gold foil experiment to help determine that nucleus of an atom that was dense and had a positive charge. During this he discovered the proton.
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Henry Moseley observed and measured the X-ray spectra of chemical elements, obtained by diffraction in crystals. He discovered a relation between wavelength and atomic number.
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Niels Bohr built a Bohr planetary model. He was able to show how electrons travel in a certain orbit.
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Francis Aston was able to determine that for some of the elements, the atomic mass was not the mass of all the atoms. This discovery was called the isotope.
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He developed an atom by mixing equations to make a mathematical model of the behavior of waves.
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He discovered the neutron. This great discovery led to the discovery of the atomic bomb.
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He discovered what makes protons and neutrons
