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460
Democritus
The first person to propose the idea that matter was not infinitely divisible. -
Issac Newton
Proposed a mechanical universe with small solid masses in motion. -
John Dalton
Proposed an "atomic theory" with spherical solid atoms based upon measurable properties of mass. -
Dmitri Mendeleev
Arranged elements into 7 groups with similar properties. He discovered that the properties of elements "were periodic functions of the their atomic weights". This became known as the Periodic Law. -
Sir Williams Crookes
Discovered cathode rays had the following properties: travel in straight lines from the cathode; cause glass to fluoresce; impart a negative charge to objects they strike; are deflected by electric fields and magnets to suggest a negative charge; cause pinwheels in their path to spin indicating they have mass. -
JJ thomson
Studied "canal rays" and found they were associated with the proton H + . -
Rutherford
He concluded that the plum pudding model was not correct because it couldn't explain the gold foil experiment. He also said that almost all the atoms positive charge and almost all of it mass were containted in a small dense region -
Albert Einstein
Published the famous equation E=mc 2 -
Aston
Discovered the existence of isotopes through the use of a mass spectrograph. -
de Broglie
Discovered that electrons had a dual nature-similar to both particles and waves. Particle/wave duality. Supported Einstein. -
Heisenberg
Described atoms by means of formula connected to the frequencies of spectral lines. Proposed Principle of Indeterminancy - you can not know both the position and velocity of a particle -
Aristole
He rejected that the notion of atoms because it did not agree with his idea of nature.
