J.J. Thomson's Experiments--At Last, I See!

When I was an undergraduate student, I believed my chemistry and physics professors hated me. I was a biological sciences major, and had to take large lecture sections with the 200-300 pre-med and pre-vet students. They were no fun as classmates. ("Will this be on the test?" they whined; later, as an instructor, I heard a pre-med choral whine of "My daddy will sue you for giving me a C.") As a student, it was almost impossible for me to ask a question in lecture, and I never got a civil (let alone helpful) answer from a chemistry or physics professor in the three years I spent in those departments.

This was in sharp contrast to my experiences in all my other classes, from Chaucer to calculus to microbiology. Of course, I graduated loving Chaucer, and statistics, and botany....and hating chemistry. Of course, every science job I ever had after grad school was in biochemistry.

Now I'm teaching a college-level chemistry class, and having flashbacks to the seventies as I prepare lectures. I'm current on DNA, but haven't thought about electron shells, subshells, and orbitals much lately. That's how I got curious about John Thomson's nineteenth century experiments on subatomic particles and electromagnetic charges. My chemistry students were supposed to work through a little computer simulation on "how we discovered the mass of the electron," but we couldn't make it "come out right." When I did this in physics lab in 1976, with equipment old enough to have been original to Thomson's lab, we got the same non-result. I couldn't make sense of it then, but I was determined to figure it out this time. That's how I came to find these excellent links. There are some amazing student resources available now. I'm a bit jealous.

• Three Experiments, One Big Idea. This is an excellent explanation from the Center for the History of Physics. I'm slowly working my way through the many interesting chemistry and physics "exhibits" on their site.
• Joseph John Thomson (1856-1940): "Carriers of negative electricity." Nobel Lecture in Physics, December 11, 1906. [from Nobel Lectures: Physics, 1901-1921 (Amsterdam: Elsevier, 1967)]. The text of Thomson's Nobel Lecture. I was amazed to find I could follow it.
• J.J. Thompson's experiment and the charge-to-mass ratio of the electron. Mark E. Tuckerman of New York University has his lectures for General Chemistry I (Honors) available on line. The Thomson experiment lecture is quite clear and readable.
• A Brief History of the Electron from Egglescliffe's Physics Website.Their information is quite comprehensible, and this is their generous mission:

  The idea behind the website is to encourage the study of physics at post-16 level and share ideas and educational material....Feel free to print/download these pages and use them in lessons / private study or starting points for www exploration. Any of the material in this website is freely available for anyone to use in their own educational web projects. If you want to acknowledge this site as a source fine, otherwise do not worry."