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200
Democritus - 440 B.C.
an Atom is a particle that cannot be cut
all atoms are small, hard particles
atoms are made of a single material formed into diffrent shapes and sizes -
Dalton
elements combined in certain proportions because they are made of single atoms
all substances are made of atoms. atoms are small particles that cannot be created, divided, or destroyed
atoms of the same element are exactly alike, and atoms of diffrent elements are diffrent
atoms join with other atoms to make new substances -
Thomson
there are small particles within an atom -
Rutherford 1909
he could see where the particles were going after hitting the gold -
Rutherford 1911
center of atom is a tiny, positively charged nucleus
positvively charged protons that passed close would be pushed away -
Bohr
electrons move around the nucleus in a certain path'
electrons can jump paths -
Schrodinger and Heisenburg
electrons do not follow a certain path
electrons paths are not preictable