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Period: 460 to 370
Democritus
He was the first person to suggest that matter cannot be infinity divided. He created the term " Atmos" to device tiny particles that make up matter. He started that atoms can't be created , destroyed or divided he never figured out what held atoms together He believed that atoms move through empty spaces. -
Period: 500 to Aug 24, 600
Aristotle
-he did not agree with Democritus's views on matter moving through empty space.
-had own views on nature
-His views caught on more than Democritus's ideas. -
Period: to
John Dalton
Was an English school teacher
Dalton's research marked the start in developing the atomic theory
Took the Democritus info, and applied it to his research
Revisee the term atom and said atoms are are the smallest particles of matter -
Period: to
Sir William Crookes
-Notable for studying cathode ray tubes
-Fundamental in the realization of atomic theory
-Made discovery in radioactivity
-Discovered Thallium -
Period: to
JJ Thompson
•Designed a series of experiments at Cambridge to determine the ratio of the particle's charge to its mass
•Disproved theory that atoms were indivisible
•Received Nobel prize for discovery of electron. -
Period: to
Robert Milikan
•Designed oil drop apparatus to determine the charge of electrons
•Charge equal to one unit of negative charge, thus electron has charge of -1
•Discovered the mass of electron using a charge/mass ratio: 9.1x10-28 -
Period: to
Ernest Rutherford
•Studied how positively charged a-particles interacted with solid matter. He designed an experiment to see if a-particles would be deflected as they passed through a piece of gold foil.
•The particles bounced at odd angles. Rutherford decided that Thompsons plum pudding model was incorrect and that the atom was just empty space for electrons to move around in.
•Eventually discovered the nucleus and protons -
Period: to
James Chadwick
• Was given the task of tracking down Rutherford's scientific evidence
• Demonstrated that the nucleus had another neutral subatomic particle
• Won the Nobel prize in 1935 for the discovery of the neutron