Wednesday, February 16, 2011
Agenda• Welcome• Announcements• Turn in Sci WB p39-40• The atomic model:
electrons & the nucleus• Lesson 1 WS (due today)• HW: Textbook p. 179:1-5
Warm Up
Draw & label an atom; what are the
charges of the parts?
I love science
Warm up answer
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PROTON - +1
ELECTRON - -1
NEUTRON - 0
NUCLEUS - positive
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Announce-mintsFebruary 14- 18
Wed - the atom; course content letter DUE
Thurs - the atom
Fri - the atom
Mon Feb 21st: NO SCHOOL!
History of the atomic model
Democritus “atoms are indivisible, solid spheres”
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John DaltonQuickTime™ and a
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The Father of the Atom
How were electrons discovered?
J. J. Thomson
Used a CATHODE RAY TUBE to discover electrons
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How were electrons discovered?
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Positive plate
Negative plate
cathode
anode
Thomson’s atomic model(chocolate chip cookie dough)
J. J. Thomson
Named the negative particles “ELECTRONS”
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Positively charge sphere with negative electrons throughout the atom
Thomson’s atomic model(chocolate chip cookie dough)
J. J. Thomson
Named the negative particles “ELECTRONS”
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Positively charge sphere with negative electrons throughout the atom
How was the nucleus discovered?
Ernest Rutherford
Conducted the Gold Foil Experiment- was a research student of J.J. Thomson
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How was the nucleus discovered?
1. Alpha particles shot through gold foil
2. Detected by screen around the foil
EXPECTEDUNEXPECTED
3. Particles were detected in unexpected places.
How was the nucleus discovered?
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Rutherford expected particles to crash through gold foil w/ little change in direction
Some particles bounced off the gold foil in ways that were not predicted by Thomson’s model
Rutherford’s Atomic Model
An atom is mostly empty space
Most of the mass is in the center of an atom
Positive charge is concentrated in the center
Electrons orbit the nucleus atany given distance from nucleus
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Practice
Lesson 1 WS (due today) Textbook p. 179:1-5
Answer the questions in COMPLETE SENTENCES
Finish for HW (due 2/17)
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