1. Thomson and Rutherford’s contributions to the model of the atom

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

3. Cathode Rays A cathode ray tube is a sealed evacuated glass tube.
Cathode rays are beams of tiny, negatively
charged particles called electrons that
flow through this 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
continued...
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
continued...
Properties Of Cathode Rays
4. The cathode rays are attracted
towards the positively charged
plate.
This tells us that cathode rays are negative.

7. EX# 1
Which of the following properties about cathode rays tell us that they are in fact negative?
The cathode rays are deflected
towards the positively charged
plate.
EX# 2
Which of the following properties about cathode rays tell us that they have mass?
The cathode rays drive a small
propeller located in their path.

8. EX# 3 EX# 4 Draw Thomson’s atomic model.- - - - - - - - -
Positive sphere with electrons embedded in it
EX# 4
What did J.J Thomson use to find the properties of electrons
The cathode ray tube and cathode rays

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

10. EX# 5 Rutherford Thomson EX# 6
Which diagram is Thompson’s and which diagram is Rutherford’s? _ _ _ _ + _
Rutherford + _
+ + _ _ + _ + _ + _ _
Thomson
EX# 6
Rutherford believed the nucleus was
POSITIVE or NEGATIVE?

11. Key Points to Remember
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