This document discusses J.J. Thomson and Ernest Rutherford's atomic models. It summarizes Thomson's cathode ray experiments that discovered the electron. Thomson believed atoms were a uniform positive sphere with electrons embedded in it. The document also describes Rutherford's model with a small, dense positive nucleus surrounded by electrons in orbit. It lists the key properties of cathode rays that revealed electrons are negatively charged and have mass.

1. Thompson and Rutherford
Objectives:
 4.5 Analyze the behaviour of
cathode rays.
 4.7 Analyze Thomson’s atomic
model.
 4.8 Analyze Rutherford’s atomic
Model

2. J.J. Thomson’s Atomic Model
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Thomson discovered the electron while
experimenting with cathode rays.
Electrons have a
negative charge
Thompson believed:
The atom was a positive sphere with
electrons embedded in it like raisins in a
plum pudding.

3. Cathode Rays
Cathode rays are beams of tiny, negatively
charged particles called electrons that
flow through this tube.
A cathode ray tube is
a sealed evacuated
glass tube.
J.J Thompson used these tubes to discover
the various properties of cathode rays
(electrons)

4. Properties Of Cathode Rays
1. The cathode rays travel in
a straight line.
2. The cathode rays drive a small
propeller located in their path.
This tells us that cathode rays have mass.

5. Properties Of Cathode Rays
3. The cathode rays cause the
shadow of the object in their
path to be projected on a
fluorescent screen.

6. Properties Of Cathode Rays
4. The cathode rays are deflected
towards the positively charged
plate.
This tells us that cathode rays are
negative.

7. Which of the properties about cathode rays
tell us that they are in fact negative?
Which of the properties about cathode rays
tell us that they have mass?
The cathode rays are deflected
towards the positively charged
plate.
The cathode rays drive a small
propeller located in their path.

8. Draw Thompson’s atomic model.
What did J.J Thompson use to find the
properties of electrons
The cathode ray tube and cathode
rays
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Positive sphere with electrons embedded in it

9. RUTHERFORD’S ATOMIC MODEL
HE BELIEVED:
the atom had a central positive nucleus
surrounded by negative electrons floating
around in a cloud like structure
Ernest Rutherford also developed
his own atomic theory

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Which diagram is Thompson’s and which
diagram is Rutherford’s?
Rutherford believed the nucleus was
POSITIVE or NEGATIVE?

11.  Thomson’s Model is known as the
plum pudding model. He also
discovered the electron.
 Memorize the four properties of
cathode rays
 Rutherford’s Model
 Positive nucleus surrounded by a fuzzy
cloud
 Electrons not organized

12. Activities
 Worksheet # 6

13. References
 Science Quest – Grenier, Daigle, Rheaume – 1998,
Cheneliere
 Student Study Guide: Physical Science 416-436(MEQ)
 Doc Brown’s Chemistry Clinic
(http://www.wpbschoolhouse.btinternet.co.uk/page04/
4_71atom.htm)
 Atom: The Incredible World
(http://library.thinkquest.org/19662/low/eng/exp-
rutherford.html)
 cwx.prenhall.com/.../ medialib/blb0202.html
 www.sci.tamucc.edu/.../ genchem/atomic/page6.htm
 library.thinkquest.org/ 3471/physics_genesis_b..
 Animation Factory
 Google Images