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Dalton
He hypothesized that all elements should be made of atoms. He proposed that all matter made of the same atoms can be combined. He said that atoms of the same element are exactly alike; he said atoms of different elements are different. Lastly he said atoms of two or more elements can be combining to form new substances. -
William Crookes
He discovered the electron. He constructed the Cathode ray which helped him discover the electron. -
Thomson
Thomson found that atoms were no simple solid spheres. He discovered electrons. -
Rutherford
He fired charged particles through a gold sheet of foil. He proposed that atoms were made of mostly space. He came up with the nucleus of an atom. He stated all of the atoms positive particles were in the nucleus. He said all of he negative atoms were in the outside of the nucleus. -
Bohr
Bohr proposed that electrons orbit around the around the nucleus. He stated that each electron has a fixed amount of energy. The electrons orbit within energy levels forming rings. They can be compared to the rungs of a ladder. -
Henry Moseley
In 1913 Henry Moseley suggested that it is the atomic number, instead of atomic weight, that identifies an atom’s properties. He made changes to the periodic table to organize the elements by their atomic weight. -
De Broglie
His ideas were a basis for developing the wave mechanics theory. This theory has greatly improved our knowledge of the physical nature on the atomic scale. -
Chadwick
He discovered the neutron.
