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Schrodinger devised and solved a mathematical equation describing the behavior of the electron in a hydrogen atom. The modern description of the electrons in atoms, the quantum mechanical model, comes from the mathematical solutions to the Schrodinger equation.

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Bohr believed Rutherford's model needed improvement. He changed Rutherford's model to include newer discoveries about how the energy of an atom when it absorbs or emits light. Bohr proposed that an electron is found only in specific circular paths, or orbits, around the nucleus.

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Rutherford wanted to test what was then the current theory of atomic structure. After testing the results were that the great majority of alpha particles passed straight through the gold atoms, without deflection. Also a small fraction of the alpha particles bounced off gold foil at very large angles. He proposed that the atom is mostly empty space, thus explaining the lack of deflection of most alpha particles. He concluded that all positive charge and almost all the mass are concentrated in a small region that has enough positive charge to account for the great deflection of some of the alpha particles. He called this region the nucleus. The nucleus is the tiny central core of an atom and is composed of protons and neutrons.

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Chadwick confirmed the existence of yet another subatomic particle, the neutron. Neutrons are subatomic particles with no charge but with a mass nearly equal to that of a proton.

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Goldstein observed a cathode ray tube and found rays traveling in the direction opposite to that of the cathode rays. He called these rays canal rays and concluded that they were composed of positive particles, called protons. Each proton has a mass about 1840 times that of an electron.

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Millikan carried out experiments to find the quantity of charge carried by an electron. Using this value and the charge to mass ratio of an electron measured by Thomson, Millikan calculated the mass of the electron. Millikan's values for electron charge and mass, reported in 1916, are very similar to those accepted today. An electron carries exactly one unit of negative charge, and its mass is 1/1840 the mass of a hydrogen atom.

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Thomson discovered the electron. Electrons are negatively charged subatomic particles. Thomson preformed experiments that involved passing electric current through gases at low pressure. After testing he found that one electrode, the anode, became positively charged. Also the other electrode, the cathode, became negatively charged.

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Dalton transformed Democritus ideas on atoms into a scientific theory. Some of the ideas included...
-All elements are composed of tiny indivisible particles called atoms
-Atoms of the same element are identical
-The atoms of any one element are different from those of any other element

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Democritus suggested existence of atoms. He believed that atoms were indivisible and indestructible.