Transcript 3.3 - JhaveriChemBioWiki

Catalyst – September (2+2)(7), 2009
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•
Please pass up COMPLETED Rap Battle
Assignment to the first person in the row
so I can stamp them.
Write a sentence describing what a
theory is.
Why weren’t cell phones invented when
regular phones were?
(Weekly Goal should already be completed)
Honors Catalyst – September 5(23-2), 2009
•
•
Please pass up COMPLETED LHC articles
to the first person in the row so I can
stamp them.
Write a sentence describing what a
theory is.
Why weren’t cell phones invented when
regular phones were?
(Weekly Goal should already be completed)
Today’s Agenda
Catalyst
 Go over Homework
 Rap Performances?
 Atomic Theory Part 1
 Work Time
 Exit Question
 Homework: Hollow Earth article

Today’s Agenda - Honors
Catalyst
 Review LHC Article
 Atomic Theory Part 1
 Work Time
 Exit Question
 Homework: Hollow Earth Article, think
about Science Fair topic and get
notebook by Monday!

Today’s Objectives
SWBAT describe the evolution of the
atomic theory from 420 B.C. to 1898.
 SWBAT compare and contrast the
contributions of Dalton and Thomson.

What is an atom?
Key Point #1: An
atom is the
smallest part of an
element that
retains (keeps) the
properties of the
element
Well then, what is an element?
Key Point #2: An element is a pure
substance that cannot be broken down
into simpler substances by physical or
chemical means
NOT THIS KIND OF ELEMENT
Well then, what is an element?
Key Point #2: An element is a pure
substance that cannot be broken down
into simpler substances by physical or
chemical means
NOT THIS KIND OF ELEMENT
Well then, what is an element?
THESE
KINDS OF
ELEMENTS
Why is the atom so important?
The atom is the building block
of all matter!
Without atoms, our universe
would no exist!
Essential Questions for Unit 3
1)
2)
3)
4)
Who made the most important
contribution to the development of atomic
theory?
What makes one atom different from
another? How are they similar?
Why is it so important to understand how
the periodic table is organized?
What secrets can we uncover about the
elements using the periodic table?
The Playas of Atomic Theory
Democritus (460-370 B.C.)
Aristotle (384-322 B.C.)
John Dalton (1808)
J.J. Thomson (1898)
R.A. Millikan (1909)
Ernest Rutherford (1909)
Niels Bohr (1913)
Chadwick (1932)
How in the World
Did These Playas
Figure All This
Out!?!
Numero Uno! - Democritus
(460-370 B.C.)

Experiment: Observations and inferences
 No
REAL experiment…just IDEAS
Where: Greece
 When: 420 B.C.
 First theory of the atom

 The
“birth” of the atom
Page 88
What were Democritus’ conclusions?
•Matter is composed of tiny
particles called atomos
•Different kinds of particles
have different sizes and shapes
•Particles move through empty
space
Numero Dos! - Aristotle
(384-322 B.C.)

Aristotle gave us this quote…
“We are what we repeatedly
do. Excellence, therefore, is
not an act but a habit.”

Among other things…
 He challenged the ideas of
Democritus
 He did not think the “nothingness” of
empty space could exist
Page 88-89
Numero Tres! - John Dalton
(1766-1844)
•Experiment:
Careful chemical
measurements
•Where: England
•When: 1803
Page 90
Dalton’s Four Postulates
1.
2.
3.
4.
All elements are composed (made up) of atoms.
It is impossible to divide or destroy an atom.
All atoms of the same elements are alike. (Ex:
One atom of oxygen is like another atom of
oxygen.) Atoms of different elements are
different. (Ex: An atom of oxygen is different
from an atom of hydrogen.)
Atoms of different elements combine to form a
compound.
Chemical reactions occur when atoms rearrange.
What were Dalton’s conclusions?
Atoms are hard,
round, solid balls.
They are similar to
marbles.
Numero Cuatro! - J. J. Thomson
(1856-1940)
•Experiment: Cathode ray
tube
•When: 1898
•Where: England
Thomson’s Cathode Ray Tube
Quick! Reading Time!
Pages 92-93
Stop at “The next significant
development….”
Thomson’s Cathode Ray Tube
Electrons are NEGATIVE!
So what does this mean about the
nature of atoms?
It was known that all matter was
neutral (no positive or negative
charge)
 So if the electron is negative, then
what does that mean about the rest
of the atom?

Thomson’s
CONCLUSIONS
•He said the atom was a ball with
electrons floating around in positive
space
•Atoms can be divided into smaller
SUBATOMIC particles!
Wait! Back to Thomson!
Now I can finish my
model! It looks like
Plum Pudding!
Work Time
On your own paper, compare and
contrast the theories of Dalton and
Thomson
 Write at least 1 paragraph (5 sentences
or more)
 Include picture of each theorist’s model.

Exit Question
1.
2.
Why do theories evolve over
time?
Do you think a theory will ever
be completely developed?
Why or why not?
Numero Cinco! - R. A. Millikan
Experiment: Millikan
Oil Drop Experiment
 When: 1909
 Where: U.S.A!!!!

Millikan’s Oil Drop Experiment
Millikan’s Calculations – Whoa!
What were Millikan’s conclusions?
I have most
accurately
measured the
charge of an
electron:
-1.59 x 10-19
Coulombs
What were Millikan’s conclusions?
I have also most
accurately
measured the
mass of an
electron:
9.109 x 10-31kg
Numero Seis! - Ernest Rutherford
Experiment: Gold
Foil Experiment
 When: 1910
 Where: Montreal

http://micro.magnet.fsu.edu/electromag/java/rutherford/
Gold Foil Experiment Explained


Alpha helium particles were shot through a piece of
gold foil
 Think aluminum foil but thinner and made out of
gold!
Alpha helium particles are 8000 times more
massive (bigger) than electrons, so Rutherford
thought they would knock electrons out of the way,
but they did not!
Remember! This is the current model of
the atom (Thanks to Thomson)
More History
Ernie’s (Rutherford) Big Adventure
Thin Sheet of Gold
Atoms
What were Rutherford’s conclusions?
Pretend you are Rutherford
 As Rutherford, what conclusion
would you make based on the
data from the Gold Foil
Experiment?

Hint: Positive repels
positive, negative
repels negative
=
What were Rutherford’s conclusions?
The deflected alpha particles
were hitting something with a
concentrated mass and
positive charge
Discovered and named the
nucleus

-
++
++
-
-
Rutherford’s Conclusion

Atoms are made of mostly
EMPTY SPACE!
 Actually,
the ratio of the size
of the nucleus to the
diameter of the orbits of
electrons can be compared
with placing a marble in the
middle of a football
stadium!
Empty Space Continued

“Neutrons and protons occupy the atom's
nucleus. The nucleus of an atom is tiny -- only
one-millionth of a billionth of the full volume
of the atom -- but fantastically dense, since it
contains virtually all the atom's mass. As
Cropper has put it, if an atom were
expanded to the size of a cathedral, the
nucleus would be only about the size of a fly
-- but a fly many times heavier than the
cathedral.” -A Short History of Nearly
Everything by Bill Bryson
James Chadwick
Experiment – Beryllium
Foil Experiment
 When - 1932
 Where – Cambridge

Conclusions – Neutral
radiation emitted;
therefore, the nucleus
contains another subatomic
particle called the neutron
(has a neutral charge)
Atomic Parts




Electron - subatomic particle with a 1- (negative)
charge
Nucleus – tiny, dense region in the center of an atom
that has a positive charge and contains most of the
atom’s mass
Proton – a subatomic particle that has a 1+
(positive) charge
Neutron – a subatomic particle with neutral (or no)
charge
PROTON
NUCLEUS
-
-
+
-
+
-
ELECTRON
-
+
+
-
-
-
NEUTRON
Compare and Contrast
What are the similarities and differences
between each contribution?
How did each theorist add to or reject the
discoveries or ideas developed before him?
RAFT - Independent Work Time
R = Role
Pretend to be either Dalton or Thomson.
A = Audience
You are writing to inform everyone of your discoveries!
F = Format
Letter, Newspaper column, or Rap
T = Topic
Details of your discovery and how you know it is true YOU HAVE “WORKED” HARD…DEFEND YOUR
RESEARCH!
Exit Ticket
1.
2.
Can people think that theories are correct even
when they are not? How does this happen? How
is it that theories change?
What was Dalton’s biggest contribution to atomic
theory?
Assignment: RAFT
Option 1: Rap
 Role: An atomic Theorist
 Audience: Writing to another atomic theorist
 Form: an appropriate rap
 Topic: Why your theory and model is better than
theirs
+3 points for presenting on Monday

Assignment: RAFT
Option 2: Polite, Formal Letter
 Role: An atomic Theorist
 Audience: Writing to another atomic theorist
 Form: a formal letter
 Topic: Politely stating why your theory and model
proves theirs wrong
+3 points for presenting on Monday

Assignment: RAFT
Things to Include



Personal information about both theorists - where
they’re from, physical appearance, etc.
All necessary facts about both theories or models
How the theory is better than the one that came
before it
Exit Question
Atomic Number
Element Symbol
Atomic Mass