Chemistry (Period 3 & 6)

Jason Stark


Course Description


Teacher: Mr. Jason Stark (email)
Room: 32 at Biomed
Supplies needed:
Composition notebook
1 Composition notebook
Binder with loose-leaf paper
3-Ringer binder with loose-leaf paper
Pen and pencil
Pens and/or pencils
Basic calculator
Basic calculator (optional)

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Recent Posts

Ring of Truth - Atoms - Light

Two key points to emphasize: 1. an input of energy isrequired to make the atoms of an atomic gas emit radiation, and 2. the radiation emitted by each element is unique.

Unit 10 Project/Presentation

Contributions to the Development of Models of the Atom

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:

  1. introduce the previous model of the atom prior to the scientist’s research
  2. the experimental design or data analyzed
  3. the evidence (data) that led to a change in the previous model
  4. how each scientist developed a new atomic model that incorporated the new evidence OR resolved a flaw in the previous model

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

Useful URL’s

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


JJ Thomson



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


Bohr - no longer there...

Oxford dictionary of scientists:  (might not be accessible outside ASU)

Access same info via:

Model assumptions:

Focus on Origin:

History, Bohr’s personal life:

What were the limitations of Rutherford’s atomic model that prompted Bohr to propose additional features?


Robert Millikan

View this video:

Could it be this one:

This one goes a little further:


Henry Mosley history/Mosely/moseley.htm


James Chadwick