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For this assignment, you will be doing some research about scientists who contributed to our current understanding of the atom. There are many scientists whose discoveries paved the way for all of us who study chemistry. You will work in groups of two or three and will be assigned one such scientist to research.
Ultimately, your goal is to write a brief story of the contribution to the development of a model of the atom that your scientist made in a way that your group can present to the rest of the class.
For each of the following scientists:
You should also find out some interesting tidbits about the scientist's life and weave those into the story you are telling about your assigned contributor. This is the one opportunity you have in chemistry to be colorful, so take advantage of it!
One class period will be devoted to preparing your story. Monday, all groups will tell their story to the class and we will create a timeline of contributions and we will trace the "model" of the atom through its historical development.
You will be graded on the content of your presentation and accompanying visual aids or diagrams as well as how well you know your story. During the presentations of other groups, you will be expected to pay attention, take notes and contribute to this whole class discussion.
Scientists: Major Experiment & Contribution:
J.J. Thomson Cathode ray tube experiments led to the discovery of the electron and plum pudding model
Ernest Rutherford Gold foil experiments led to the discovery of the atomic nucleus and an update to the model of the atom
Robert Millikan Oil drop experiments led to additional information about the charge and mass of electrons
Henry Moseley Observed x-rays emitted by different elements, which led to the discovery of the atomic number
Sir James Chadwick Used a beryllium foil experiment to discover another particle in the atom that was hard to find
Niels Bohr Observed the emission spectrum of hydrogen to create a model of the atom that now bears his name
Timeline (View the proper sequence of the evolution of the model of the atom.)
Here is an overview of the development of the modern model of the atom
Follow the instructions while viewing this simulation of Rutherford’s experiment.
Here is another simulation that illustrates the Gold Foil experiment.
Which atomic model is used to illustrate the experiment ?
Why is this atomic model used instead of the Thompson’s (previous model)?
More information on Rutherford’s Model
http://zebu.uoregon.edu/~imamura/208/jan27/hup.html - no longer there...
Oxford dictionary of scientists: http://www.oxfordreference.com/view/10.1093/acref/9780192800862.001.0001/acref-9780192800862-e-161?rskey=a5PXwO&result=161&q= (might not be accessible outside ASU)
Access same info via: http://www.answers.com/topic/niels-bohr
Model assumptions: http://chemed.chem.purdue.edu/genchem/history/bohr.html
Focus on Origin: http://en.wikipedia.org/wiki/Bohr_model
History, Bohr’s personal life: http://www.nobelprize.org/nobel_prizes/physics/laureates/1922/bohr-bio.html
What were the limitations of Rutherford’s atomic model that prompted Bohr to propose additional features?
View this video:
Could it be this one: http://www.youtube.com/watch?v=XMfYHag7Liw
This one goes a little further: http://www.youtube.com/watch?v=UFiPWv03f6g
J.J. Thomson performed experiments with cathode rays in an attempt to understand electricity – which was still a mystery in the late 1800s. Review the website A Look Inside the Atom http://www.aip.org/history/electron/jjhome.htm to find the conclusions that Thomson and other physicists drew regarding the mysterious cathode rays.
Thomson’s 1897 Experiments - state the conclusions Thomson drew from each of his famous cathode ray experiments:
Thomson’s Atomic Model: Thomson presented three hypotheses from his experiments. Only two were accepted by physicists – in fact the third was shown to be wrong! From the first two came a model of the atom known as the Plum Pudding model. Complete the atom drawing below to illustrate Thomson’s plum pudding model. Explain how this fits with his observations.