Download Notes 4.1 In the fourth century BC, the Greek philosopher

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Notes 4.1
In the fourth century BC, the Greek philosopher Democritus suggested
that the universe was made of indivisible units. This suggestion did not
have any evidence.
As thinkers and technology improved more data was collected and
theories were developed.
Daltons Atomic Theory stated that all atoms of a given element were
exactly alike, and atoms of different elements could join to form
compounds. Dalton’s theory is considered the foundation of the
modern atomic theory.
THE LAW OF DEFINATE PROPORTIONS states that a chemical compound
always contains the same elements in exactly the same proportions by
weight or mass.
Thompson’s Model of the Atom suggested that atoms were not
invisible. He was experimenting with electricity and the mysterious
rays in a vacuum tube.
Thompson’s model is called the Plum Pudding Model because of the
popular dessert of the day and how the atom was represented.
Rutherford’s Model of the atom stated that most of the mass of the
atom was concentrated at the atoms center. He directed positive
charged alpha particles at a piece of gold foil and recorded the results.
Rutherford discovered the nucleus of the atom by recording the
deflection of alpha particles that passed or were deflected in his gold
foil experiment.