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Democritus created the theory of Atoms and the Void. He believed that matter was made up of tiny, indivisible particles of different shapes and sizes. They floated around in an infinite nothingness called the void, repelling or attracting each other and colliding. *Date not specific. Circa. 460 BCE
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Isaac Newton devloped the laws of motion, and the laws of gravity. This would lead to later scientists defining the laws of physics.
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Dalton proposes the atomic theory, with spherical, solid atoms based upon measurable properties of mass.
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G.J. Stoney, an Irish scientist, proposes that electricity was made of negative particles called "electrons" *Date not specific
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Using cathode ray tubes, J.J Thompson, an English scientist, determines the existance of light particles that make up the atom. He confirms the existence of the electron. *Date not specific
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Planck, a German scientist, creates the Quantum theory. *Date not specific
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Nagaoka postules a Saturn-like model of the atom, with flat rings of electrons orbiting around a postively charged nucleus. *Date not specific
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Using an oil drop experiment, Milikan, an American scientist, determines that mass and charge of an electron
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E. Rutherford published his atomic theory that described the atom as mostly empty space which included a central nucleus positively charged orbited by negatively charged particles called electrons.
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Using x-ray tubes, H.G.J, Mosely determined the charges on the nuclei of most atoms. He found that the atomic number of an element is equal to the number of protons in the nucleus.
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Bohr learned that chemical properties of matter depended on the frequency and arrangement of electrons around the nucleus. This meant that the elements on the periodic table should be arranged by number of electrons, rather than atomic weight, as previously thought.
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In 1932, an English scientist named James Chadwick discovered the existance of the neutron.