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450
Democritus
- Created notion of the atom -A piece of matter that is the smallest part "Atomas" -Anciet Greece -450 B.C. -Democritus predicted that atoms cannot be destroyed, differ in size, shape and temperature, are constantly moving, and are invisible. He believed that there are an infinite number of atoms. This hypothesis was created in 465BC. -He published over 70 books -He lived to be 90 years old
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450
Aristotle
-Ancient Greece
-450 B.C.
-All substances made of 4 elements
-Earth, Wind, Fire, Water
-He thought that all materials on Earth were not made of atoms -
John Dalton
- English- 1780's
- " Father of atomic theory"
- Atoms make up elements
- Atroms of the same element are identical
- Atoms of different elements are different
- Atoms of different elements react to form compounds
- Atoms can not be created or destroyed only changed -Believed that Democritus was on the right path not Aristotle
- He has the same model as Democritus -When John Dalton died, 40,000 people attended his funeral procession. -He discovered color blindness
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J.J. Thomson
-Found a negative particle also known as the electron
- Cathode Ray Tube Experiment
- Plum pudding model
- " chocolate chip cookie model"
- Adopted because it showed that the atom must have a negative particle -
Henri Becquerel
-Discovered radioactivity
- Lead container experiment looked at how gamma rays were effected by plates
- Showed that atoms must have to charged particlees both positive and negative becasue of his electon decay in his experiment -
Marie & Pierre Curie
-discovered radium and polonium
-investigated radioactive substances
-contributed to x-rays
-pioneering research on radioactivity
- furthered Becqurel's research. -
Robert Millikan
-Famous for Oil Drop Experiment.
-Professor at University of Chicago
-Also studied in Germany
-Model proved that there must be a positive charge in an atom because in his oil drop experiment it netralized the electron like the atom does.
- Worked with Einstein on Photoelectric effect
-Also worked with cosmic ray physics -
Ernest Rutheford
-Gold Foil Experiment
- Beleived in very small dense positive center also known as the nucleus
- electron cloud model
-He was born with a umbilical hernia which killed him when it was left untreated for too long.
-He was denied permission to teach each time he applied for a job
-One of the elements, Rutherfordium (element number 104) is named after him -
Niels Bohr
-Added understanding to quantum mechanics and atomic structure.
-Believed that atomhad a nucleus in the center surrounded by electrons.
-Wokred on the idea that elecrons jump form one level to another.
-Dansih physicist. -
Quantum Model
- Looked at the Bohr model and extended it.
- found that electron levels had a certain amount of electrons tha they could hold. -Scientists involved incldeed Max Plank and Albert Einstein as well as Neils Bohr.
- Electorns levels are electron orbitals.
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James Chadwick
- Dicovered the neutron -Worked on the Manhattan Project -Answered what the other particle was in the nucleus
- It is accurate because the particle is neither positive or negative. -October 1891- July 1974
