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/rutherford

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 )

Atomic Structure