Atomic Structure

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Atomic Structure
Daniel R. Barnes Init sometime about a year
before 10/4/2006
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SWBAT . . .
. . . describe what atoms are made of, in terms
of size, mass, electric charge, location, and
motion.
SWBAT Students will be able to
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SWBAT . . .
. . . explain how theories and laws evolve over
time.
SWBAT Students will be able to
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Click the link!
http//primaxstudio.com/stuff/scale_of_universe/in
dex.php
When you click the link above and play with the
slider on the scale of the universe thingie, make
sure to go all the way down to the size of
molecules, atoms, the nucleus, and individual
protons, neutrons and electrons. You really need
to see just how small that stuff is.
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Anything that takes up space and has mass.
Solids, liquids and gases.
ORDINARY matter, not dark matter or dark energy.
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What is matter made of?
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is made of
ATOMS
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If matter is made of atoms . . .
What are atoms made of?
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Atoms are made of . . .
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Atoms are made of . . .
Subatomic Particles
Subatomic Particles
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10 9 8 7 6 5 4 3 2 1 0 -1 -2 -3 -4 -5 -6 -7 -8 -9
-10
Subatomic Particles
What does subatomic mean?
Sub- means below or under.
When you start giving number values to altitude,
whether youre talking about airplane altitude or
the number of the floor in a building, under
starts to mean . . .
less than.
On the vertical number line to the right, 2 is
below 3 because 2 is less than 3.
A submarine goes underwater.
A subatomic particle is a speck of matter that is
less than an atom.
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10 9 8 7 6 5 4 3 2 1 0 -1 -2 -3 -4 -5 -6 -7 -8 -9
-10
10 9 8 7 6 5 4 3 2 1 0 -1 -2 -3 -4 -5 -6 -7 -8 -9
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Subatomic Particles
What does subatomic mean?
Sub- means below or under.
If the number line to the right were a
thermometer, temperatures below zero would be
called . . .
. . . sub-zero temperatures.
Sub-zero is below zero.
Sub-zero is less than zero.
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Subatomic Particles
What does subatomic mean?
A subatomic particle is less than an atom.
A subatomic particle is just a part of an atom.
There are three subatomic particles you have to
get to know . . .
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Subatomic Particles
proton
mass 1.007 amu
charge 1
mass 1.009 amu
neutron
charge 0 neutral
mass 0.000549 amu
electron
charge -1
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Electrostatic Forces
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Electrostatic Forces
Youre repulsive!
Youre rePULsive!
?
repulsion
?
repulsion
?
attraction
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Electrostatic Forces
?
no reaction
?
no reaction
Bringing a charged object near a neutral object
can cause the neutral object to develop -
zones, which can make the neutral object
attracted to - objects, so my jury is not yet
out on neutrons . . .
?
no reaction
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Which two particles are the heaviest?
proton
mass 1.007 amu
mass 1.007 amu
charge 1
mass 1.009 amu
neutron
mass 1.009 amu
charge 0 neutral
mass 0.000549 amu
mass 0.000549 amu
electron
charge -1
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Historical Trivia Time!
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Who discovered the electron?
Joseph John Thomson, 1897
He didnt do all the work, though.
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Crookes tube
William Crookes 1832-1919
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magnet
A normal dry cell (battery) only provides 1.5
volts. This experiment required thousands of
volts.
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Electron momentum or radiometric effect?
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Who discovered the nucleus?
Ernest Rutherford, 1911
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1909
omfg!
Hans Geiger
Ernest Marsden
ZnS
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Imagine a marble on the 50-yard line.
Thats how small the nucleus of an atom is
compared to the atom as a whole.
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SWBAT . . .
. . . draw atoms correctly.
SWBAT Students will be able to
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Let's draw an atom.
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neutral, so

3
Li
atomic number
3
3 Li 6.94
7S
-3
average atomic mass
4
mass number
S Sigma
Sigma is a symbol used in math science. It
means sum or total.
nucleus
CLICK ME to see the atomic masses of the isotopes
of oxygen.
mass protons neutrons
"shell" or "energy level"
neutrons mass - atomic
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neutral, so

3
Li
3
3 Li 6.94
7S
-3
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nucleus
Which two particles are the heaviest?
Where is almost all the mass located?
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Materials reminder
Got graph paper?
Youll need it next week
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real rabbit
cartoon rabbit
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real atoms
(same picture as page 103 in section 4.1 of your
book)
cartoon atom
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?
?
?
?
?
?
Cartoon electron orbit
More realistic electron orbit
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nucleus
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So, whats wrong with the way I drew this atom?
The nucleus is far too large. Lets shrink it.
Is that small enough?
Okay. Lets shrink it again, then.
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Is that small enough for you?
An atom may be tiny, but its gigantic compared
to the nucleus in its center.
Lets shrink it again, then.
Empty space
Okay. Is THAT small enough?
Thats pretty strange, considering that the
nucleus is where over 99 of the atoms mass is.
Why not?
Yep. If you can see it, I drew it too big.
Atoms are made mostly of . . .
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Is that small enough for you?
An atom may be tiny, but its gigantic compared
to the nucleus in its center.
Lets shrink it again, then.
Empty space
Okay. Is THAT small enough?
Thats pretty strange, considering that the
nucleus is where over 99 of the atoms mass is.
Why not?
Yep. If you can see it, I drew it too big.
Atoms are made mostly of . . .
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Empty space
And youre made of atoms, so . . .
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Hey, Mr. Barnes! I got a question!
. . . YOURE made mostly of empty space.
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If Im made mostly of empty space,
And youre made mostly of empty space . . .
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How come it hurts so bad when I kick you in the
nuts?
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Since were made mostly of empty space, youd
think wed just pass through each other like
ghosts.
Instead, we bounce off of each other like
billiard balls.
Why is that?
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Ask me again when weve done the static
electricity lab.
Okay. Can we go to the Did you get it
questions, then?
We HAVE done the static electricity lab! Explain!
Explain!
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Do you remember what happened when we charged up
both balloons and tried to bring them close
together?
Think about that for a bit while we imagine me
kicking a wall.
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An atom in my foot
An atom in the wall
As my foot gets closer and closer to the wall,
what parts of the atoms come into contact first?
The electrons are on the outside of the atom, so
theyre the parts that come closest together.
The electrons are the ambassdors of an atom.
Lets forget about the atoms and just focus on
the electrons.
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Yes we do, and you just hurt mine!
I dont care if youre sorry.
Youre gonna hear from my lawyer!
An electron in the wall
An electron in my foot
How do electrons feel about each other?
Theyre both negatively-charged, so . . .
Well,
okay, they repel each other. Electrons dont
really have feelings.
They hate each other.
So, anyway, electrons push each other away. They
feel an electrostatic repulsion for each other.
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An electron in the wall
An electron in my foot
In order for my foot to get closer to the wall, I
have to exert force to get my electrons to get
closer to its electrons.
The force my muscles exert has to be at least as
strong as the repulsion between our electrons.
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An electron in the wall
An electron in my foot
Charge on the first object
Charge on the other object
Theres an equation that predicts the electrical
force between two charged objects. It looks a
lot like Newtons law of universal gravitiation.
kQ1Q2
Fe
R2
Electrostatic Force
Distance between the two objects
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According to the equation, if the charge of
either particle gets larger, the force gets
larger also.
An electron in the wall
An electron in my foot
(
)
When the numbers on the top of a fraction get
larger, the value of the fraction gets larger.
kQ1Q2
Fe
R2
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According to the equation, if the distance
between the objects gets larger, the force gets
weaker.
An electron in the wall
An electron in my foot
(
)
When a number on the bottom of a fraction gets
bigger, the value of the fraction gets smaller.
kQ1Q2
Fe
R2
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If you make a graph of force versus distance . .
.
Its a downward-swooping curve.
An electron in the wall
An electron in my foot
Force (Fe)
kQ1Q2
Fe
R2
Distance (R)
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The closer the two electrons get . . .
the stronger the repulsive force between them
gets.
An electron in the wall
An electron in my foot
Force (Fe)
kQ1Q2
Fe
R2
Distance (R)
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Lets imagine the electrons getting as close as
possible, close enough to touch.
Whats the distance between two touching objects?
If two objects are touching, there is no longer
any distance between them.
An electron in the wall
An electron in my foot
In other words, if two objects are touching, R
0.
kQ1Q2

Fe
If the number on the bottom of a fraction equals
zero, what is the value of the fraction?
R2
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So, to get my atoms to get close enough to touch
the walls atoms, I have to exert an infinite
amount of force in order to overcome the
electrostatic repulsion between my electrons and
its electrons.
Im just not that strong.
It may look like my foot touches the wall when I
kick it, but actually, my foot never really does
touch it.
My foot gets really close to the wall, but the
outside surfaces of my atoms never quite touch
the outside surfaces of the walls atoms before
they bounce back.
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Well, that was a fun little mental tangent, but
lets get back on track and see if weve lived up
to our SWBATs for this lesson . . .
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Did you get it?
Q1 What are the three main subatomic particles
that atoms are made of?
A protons neutrons, and electrons
Q2 Where are protons, neutrons, and electrons
found?
A Protons and neutrons are found in the
nucleus. Electrons orbit the nucleus, grouping
into shells.
Q3 Compare the masses of protons, neutrons, and
electrons.
A Protons and neutrons have a mass of about 1
amu each. Electrons weigh much less (only
1/1836th of an amu each).
Q4 Compare the electric charges of our
subatomic particles.
A Protons are 1, neutrons are neutral (zero),
and electrons are -1.
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Did you get it?
Q5 How do the various subatomic particles feel
about each other?
A Protons repel protons and electrons repel
electrons. Protons and electrons attract each
other. Neutrons dont care about anyone else,
and the feeling is mutual.
Q6 Describe the charge, mass, and volume of the
nucleus, in comparisson to the atom as a whole.
A Although over 99 of an atoms mass is
crammed into its nucleus, the nucleus is so small
compared to the atom as a whole that it is like a
marble compared to a football stadium. The
nucleus is positive because of the protons in it.
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THINK-PAIR-SHARE
TPS1 What did Rutherford discover about the
anatomy of an atom, and how did he do it?
A By shooting alpha particles at gold foil,
Rutherford discovered that there is a very small,
dense, positively-charged particle in the center
of an atom. He called it the nucleus.
TPS2 How did Rutherfords discoveries build
upon what his mentor, J. J. Thomson, had
discovered?
Thomson discovered the electron, but he
mistakenly believed that the positive charge in
an atom was spread evenly throughout its volume.
Rutherford showed that the positive charge was
concentrated in a very small dot in the center.
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Materials reminder
Got graph paper?
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R.I.P. . . ?
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Password cougar1
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The End
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Time to draw some more atoms
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neutral, so

1
H
2
1
1 H 1.01
2S
-1
1
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, so 4 2
2 missing
2
2
Be
4
4 Be 9.01
9S
-4
5
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10
, so 8 2
2 extra
2-
O
8
8 O 16.00
16S
- 8
8
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9
, so 6 3
3 extra
3-
C
13
6
6 C 12.01
13S
- 6
7
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It aint over til the lady with the shoe on her
head says its over.
Its over.
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Here is the Los Angeles Memorial Coliseum as seen
from a satellite.
Click here to go to the website from which this
image was taken.