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From ancient Greece, Democritus created the idea of the atom, making the foundation for others to come. He believed that all matter was made of atoms, which were indestructible and varied in size and shape.
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The model Democritus came up with was a sphere.
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Born in Eaglesfield, England, Dalton continued with the idea of the atom, using prior knowledge to come up with these ideas:
Matter is made of atoms, which are indivisible.
All atoms of one element have the same mass and properties.
Compounds are combinations of different kinds of atoms.
A chemical reaction is atoms being rearranged. -
Dalton's model of the atom was a sphere.
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Born in Cheetham Hill, England, J.J. Thompson discovered the electron through experimentation.
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This model is called the Plum Pudding model. It shows electrons floating in an area of positivity.
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Thompson experimented with cathode ray tubes. When high voltage is sent across the cathodes at the end of a cathode ray tube, a beam of particles goes from the cathode to the anode. Thompson put two oppositely charged electric plates around the cathode ray, which deflected away from the negatively charged plate and towards the positively charged one. This showed that the particles, electrons, were negatively charged.
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Born in Nelson, New Zealand, Ernest Rutherford discovered the nucleus.
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Rutherford's atomic model showed a small nucleus surrounded by empty space.
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Rutherford fired a beam of alpha particles at a gold sheet. He put radium in a lead box with a pinhole. The lead absorbed most of the radiation but a small beam of particles went out the keyhole towards the foil. A few alpha particles were deflected from their path. This showed that the positive charge must only be in a small part of the atom, and the rest is empty space.
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This model showed electrons moving in orbits called energy levels around the nucleus.
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Born in Copenhagen, Bohr improved the atom model even further. In 1922, he won the Nobel Prize for this work. He was the head of Theoretical Physics at Copenhagen University for forty years, from 1920 to his death.
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This model shows the probability of the position of an electron by showing a nucleus surrounded by an electron cloud. The electron cloud shows where electrons might be found.
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Schrödinger updated the model of the atom by creating the Quantum Mechanical Model. He also spent time learning about many other subjects such as Italian painting and botany. In World War I, he was an artillery officer.
