Download Atomic Structure

Atomic Structure
• Discovery of the
electron
– In 1897, JJ Thomson,
an English physicist
began studying
atomic structure using
a cathode ray tube
(see right)
Thomson continued
• How did the experiment work??
• Thomson deflected the cathode ray using an
electrical field, resulting in the ray bending toward
the positive pole, so……the ray had to be made of
negative particles, called electrons
Thomson Conclusion
• But I thought the atom
was neutral???
– It is!! Thomson knew
that there must be a
source of positive
energy, but wasn’t
quite sure how it fit in.
– So he developed the
first model of the atom
(on right) which he
called Plum Pudding
Millikan and his oil drops
• Robert Millikan did
some pretty neat
experiments with oil
drops to determine
the mass of an
electron to be 9.1 x
10-31 kg.
Phase 2---Ernest Rutherford
• Rutherford was a student of Thomson’s
• Weaknesses of Thomson’s model
• Rutherford tries to expand Thomson’s
model to make it more complete
Rutherford continued
• In 1911, Rutherford
designed an
experiment to test
Thomson’s theory
called the gold foil
experiment (see right)
More Rutherford
• micro.magnet.fsu.edu/electromag/java/ruth
erford
Enough Rutherford, already!!
• After all was said and
done, Rutherford’s
final model of the
atom looked
something like this
Niels Bohr
• Knew Rutherford’s
model couldn’t be
completely correct or
the electrons would
crash into the nucleus
• So he proposed the
electron energy level
model
Finally! The Quantum Theory
•
•
•
•
•
Bohr’s model was very restrictive
Are atoms REALLY that well-behaved?
Louis de Broglie….wave or particles??
Walter Heisenberg and his uncertainty..
What is an orbital anyway??
Last, but not least!!
• So what does an
atom actually look
like?? (at least for
now )