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400
Democritus
His theory revolves around the atoms that are present in all forms, solid or liquid. The theory states that these atoms are all individually created an can't be separated. This creates the beginning of the Atomic Theory. -
400
Democritus model
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Period: 400 to
Years
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John Dalton
Dalton's theory states that all matter is made up of atoms and that atoms are indivisible and indescructible. All atoms of a given element are identical in mass and properties. Compounds are formed by a combination of 2 or more different kinds of atoms. Dalton's theory also includes that a chemical reaction is a rearrangement of atoms. -
John Dalton model
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Dmitri Mendeleev
Dmitri arrangedthe the 63 known elements into a Periodic Table based on atomic mass. His Periodic Table arranged the elements in order of atomic weight and grouping them by their properities. He also left some space for undiscovered elements for future scientists. -
Dmitri Mendeleev model
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JJ Thomson model
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Max Planck
Max formulated an equation describing the blackbody spectrum. Planck believed that energy was directly proportional to frequency (E=hv). Planck also got the Nobel Prize in 1918 for his quantum theory after it had been successfully applied to the photoelectric thoery. -
Max Planck Theory
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JJ Thomson
In 1904, Thomson suggested a model of the atom as a sphere of positive matter where electrons are positioned by electrostatic forces. He estimated the number of electrons in an atom from measurements of the scattering of light. -
Robert Millikan oil drop
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Robert Millikan
His oil drop experiment determined the charge carried and the mass of an electron using the falling-drop method. Robert verified Einstein's photoelectric equation. -
Ernest Rutherford
Ernest Rutherford publishes his atomic theory describing the atom as having a central positive nucleus surrounded by negative orbiting electrons. This suggested that most of the mass of the atom was contained in the small nucleus, and that the restt of the atom was mostly empty space. He came to ths conclusion following the results of his famous "gold foil experiment" -
Rutherford's gold foil experiment
The Gold Foil experiment shot minute particles at a thin sheet of gold. A small percentage of the particles were deflected while a majority passed through the sheet. This concluded that the mass of an atom was concentrated at its center. -
Henry Moseley
Henry showed that periodicity was a fucntion of the atomic number rather than of atomic mass, the physical and chemical properties of the elements are periodic functions of their atomic numbers. He contributed towards physics through his research. -
Henry Moseley periodic table
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Neils Bohr
Neil developed an explanation of atomic structure. His atomic model had atoms built up of orbital shells of electrons. Borh won a Noble Prize in 1922 for his work with the structure of atoms. -
Neils Bohr
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Louis de Broglie
Louis de Brogle discovered that electrons had a dual nature-similar to both particles and waves. He supported Einstein and changed the view of the physical world by showing matter is a form of enegry in itself. -
Louis de Broglie model
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Werner Heisenberg
Werner proposed Principle of Indeterminancy and said atoms are connected to the frequencies of spectral lines. This states you can not know both the position and velocity of a particle. -
Werner Heisenberg formula
