Thomson, Plum Pudding Model, & Rutherford notes
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Thomson’s Experiment
J.J. Thomson used a cathode ray
tube to show that the atoms of any
element can be made to emit tiny
negative particles.
He knew the particles were
negative because they were
repelled by the negative part of an
electric field.
He concluded that all types of
atoms must contain these negative
particles.
These particles are now called
ELECTRONS.
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Rutherford’s
Ernest Rutherford, a student of J.J.
Thomson, designed the gold foil
experiment.
The gold foil experiment design
directed alpha particles at a piece
of gold foil. The gold foil was
surrounded by a screen that made
tiny flashes when it was hit by an
alpha particle.
Most of the alpha particles passed
through the gold foil, but some of
the alpha particles were deflected
at an angle.
The Plum Pudding Model
J.J. Thomson and Lord Kelvin
proposed that the atom might be
something like a plum pudding (a
pudding with raisins randomly
distributed throughout).
They reasoned that the atom was
a positively charged with negative
electrons scattered throughout to
counterbalance the positive
charge.
Experiment
 His conclusion was that the Plum
Pudding Model could not be
correct. That the large deflections
of alpha particles could only be
caused by a center of concentrated
positive charge that would repel
the positively charged alpha
particles.
 Most of the particles passed
through the foil directly because
the atom is mostly open space.
 We now call this concentrated
center of positive charge the
NUCLEUS and the electrons travel
around the nucleus in mostly
empty space.