Atomic History MentorMob Tutorial
http://www.mentormob.com/learn/i/atomic-theory/atomic-theory-timeline
Step 1: Timeline and Intro to Atomic History

On the timeline below, write in the following events and years.
1-Small parts of matter are proposed.
2- The Atomic Theory is published
3- Electrons are discovered using the cathode ray tube
4-Charge of an electron discovered
5-The gold foil experiment proves the existence of an atomic nucleus
6- Neutrons discovered

Write the name of the scientist next to each great atomic discovery.
_______________________ Small parts of matter are proposed
_______________________ The Atomic Theory is published
_______________________ Electrons are discovered using the cathode ray tube
_______________________ Charge of an electron discoverd
_______________________ The gold foil experiment proves the existence of an atomic nucleus
_______________________ Neutrons discovered
Step 2: Democritus’s Contribution
Who was Democritus’s fiercest opponent?
Why do you think Democritus’ ideas accepted by the world until almost 2000 years later?
Draw a picture of what you think Democritus believed an atom looked like:
Step 3:Dalton’s Contribution
Summarize the 6 key points in Dalton’s atomic theory:
1. ________________________________________________________________________
2. _______________________________________________________________________
3. ________________________________________________________________________
4. ________________________________________________________________________
5. ________________________________________________________________________
6. ________________________________________________________________________
Were all of Dalton’s steps correct? Explain briefly…
Step 4: Thomson’s Contribution
Play and watch the video. What is a cathode ray tube?
Draw what happens to the particles in the cathode ray when a negatively charged plate (or
magnet!) is placed nearby:
Plate with - charge
Cathode
Ray Tube
Plate with + charge
What subatomic particle (proton, neutron, or electron) was discovered using this experiment?
Step 5: Milikan’s Contribution
Follow the instructions on the webpage to go through the simulation of Milikan’s Oil Drop
Experiment.
What happens to the oil drop as the voltage increases?
Read the text below the simulator. What did Milikan discover by doing this experiment?
Step 6: Rutherford
Watch the video.
List the important materials used for the experiment:
What did Rutherford discover by doing this experiment?
Draw, to the best of your ability, a representation of how the gold foil experiment is set up. (use
other internet sources to help you if needed)
Step 7: Quiz! What Do You Know About Atomic Theory?
Democritus' idea of matter made of smaller parts was not accepted because he did no experiments.
True
False
Which of the following is NOT part of Dalton's atomic theory?
Atoms of the same elements are the same.
Atoms combine in whole number ratios to create compounds.
Quarks are the smallest particles that can cause reactions.
All matter is made of small, indivisible particles called atoms.
Dalton's atomic theory was correct.
True
False
Which atomic scientist worked with the cathode ray tube?
Rutherford
Millikan
Thomson
Dalton
The cathode ray bent away from a negative electric field. This means that the cathode ray is made of which of
the following?
positive protons
positive electrons
negative protons
negative electrons
Millikan's oil drop experiment determined the charge on the electron.
True
False
Rutherford's gold foil experiment led to the realization of which view of the atom?
a tiny, dense nucleus with lots of empty space
tiny negative particles spread evenly through positive matter.
tiny positive particles spread evenly through negative matter
a large, empty center with a lot of negative matter circling it