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492
Democritus- 492 BCE
Democritus’ greatest contribution was the atomic theory he elucidated (not called atomic theory at the time). Democritus was the first person to think of the idea of the atom
His theory was that the universe and all matter followed certain principles
The principles were that everything is composed of atoms which are physically, but not geometrical indivisible -
Period: 492 to
Atomic Theory
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John Dalton
John Dalton’s greatest contribution was quite obviously that he was the first to suggest an “atomic theory” with spherical solid atoms based on measurable properties of mass. He believed that all matter was made of atoms that were indestructible.
He also believed that all atoms of a certain element are identical in mass and properties/features.
As well as these, he believed compounds are formed by 2 or more different kinds of atoms and that any chemical reaction is a rearrangement of atoms. -
J. J. Thompson
Joseph John Thompson’s largest contribution was that he was the one to discover the electron. He discovered the electron in the middle of a series of experiments designed to study the nature of electric discharge.
He interpreted the reflection of rays by electrically charged plates and magnets to prove that energy is much smaller than a size of an atom. -
Robert Millikan
Millikan’s greatest contribution was that he determined the unit charge of the electron. He determined this with his oil drop experiment.
This contributed to the ability of calculating the mass of the electron and the positively charged atom. -
Ernest Rutherford
Ernest’s largest contribution was that his atomic theory described that the atom had a central positive nucleus. He also suggested that it is surrounded by negative biting electrons. The model he created suggested that most of the atoms mass was contained in the nucleus and the rest is just an empty space He came to this conclusion following his gold foil experiment -
Werner Heisenberg
Heisenberg’s contribution was the Uncertainty Principle. The uncertainty principle basically states that you can not know all the properties of an atomic particle.
For example, the more certain you are of it’s position, the less you are about it’s momentum.
