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Democritus
- - a greek philiosphoer in 440 B.C
- - Came up with the Concept of the Atom
- - HE said that atoms were small, hard particles that were uncuttable.
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John Dalton
- - he developed an atomic theory based on oberservations gathered from many experiments from combining elements
- - his theory was: all substances were made of atoms. ( atoms are small particles that cannot be created, divided, or destroyed.
- - atoms of the same element are alike and atoms of different elements are different.
- -atoms join with ather atoms to create new substances
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J. J Thomson
- - was the first person that atoms can be divided
- -He experimented with a cathode blue- tube
- - he called negetivly charged articles corpuscles ( we now call them electrons)
- - he did the plum pudding model to show the atom with negetivly charged electrons
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Ernest Rutherford
- - first to discover that atoms had a small, dense nucelus than contained posititvely charged
- -Gold foil experiment- aimed charged particles at a thin sheet of gold foil( trying to see where postitive charges would go)
- - Positively charged particles passed close to the nucleus were deflected away( if it hit the nucleus in would come almost straight back.)
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Rutherford's "Planetary Model"
- Atoms
- - is mostly empty space so electrons travel throught it
- -has a small, dense postitivley charged nucleus
- -electrons travel around the nucleus like planets around the sun.
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Current theory- Electron Clouds Schrodinger and heisenberg.
- - they explained that electrons do not travel in definite paths.
- - electrons paths cannot be predicted .
- -The current theory suggest that electrons are found in regions called electron cloud.
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Niels Bohr
- - In 1913 Niels bohr determined that electrons traveled around the nucleus in definite paths.
- -He also discovered that electrons could jump from on path in one level to a path in another level
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