Transcript Daniel R. Barnes Init: sometime about a year before 10/4/2006

Daniel R. Barnes
Init: sometime about a year before 10/4/2006
. . . describe what atoms are made of, in terms of
size, mass, electric charge, location, and motion.
“SWBAT = “Students will be able to”
. . . explain how theories and laws evolve over
time.
“SWBAT = “Students will be able to”
http://scaleofuniverse.com/
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.
Thank you, Francisco Lerma and Aranza Guzman for helping me fix the link! DRB 9/8/2014
9
8
7
6
What does “subatomic” mean?
5
4
“Sub-” means “below” or “under”.
3
2
When you start giving number values
1
to altitude, whether you’re talking
0
about airplane altitude or the number
-1
of the floor in a building, “under”
-2
starts to mean . . . “less than”.
-3
On the vertical number line to the
-4
right, “2” is below “3” because 2 is
-5
less than 3.
-6
A subatomic particle
is a speck
A submarine
goesof
underwater. -7
-8
matter that is less than an atom.
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.
9
8
7
6
5
4
3
2
1
0
-1
-2
-3
-4
-5
-6
-7
-8
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 . . .
mass = 1.007 amu
charge = + 1
mass = 1.009 amu
charge = 0 = “neutral”
mass = 0.000549 amu
charge = -1
You’re
repulsive!
You’re
rePULsive!
repulsion
repulsion
attraction
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
Which two particles are the heaviest?
mass = 1.007 amu
charge = + 1
mass = 1.009 amu
charge = 0 = “neutral”
mass = 0.000549 amu
charge = -1
Who
discovered
the electron?
Joseph John
Thomson,
1897
He didn’t do
all the work,
though.
Crookes tube
William Crookes
1832-1919
magnet
NOTE: A normal dry cell (“battery”) only provides 1.5 volts.
This experiment required thousands of volts.
Electron momentum or radiometric effect?
This is more or less a picture of Thomson’s “plum pudding”
model of the atom.
It’s an improvement over Democritus’ and Dalton’s models in
that it states that an atom CAN be broken into pieces.
Who
discovered
the nucleus?
Ernest
Rutherford,
1911
1909
omfg!
Hans
Geiger
Ernest
Marsden
ZnS
Imagine a marble on the 50-yard line.
That’s how small the nucleus of an
atom is compared to the atom as a
whole.
This cartoon
drawing of an
atom is largely
based on the
“solar system”
model of the
atom that
Rutherford came
up with after the
gold foil
experiment.
It’s full of flaws,
but it was an
improvement on
Thomson’s
“plum pudding”
model.
Note that the
nucleus in this
cartoon is shown
as being
far too . . .
BIG.
(Remember the
marble on the 50
yard line!)
Materials reminder:
Got graph paper?
You’ll need it next week
real rabbit
cartoon rabbit
real atoms
(same picture as page 103 in section 4.1 of your book)
cartoon atom
Cartoon electron orbit
More realistic electron orbit
So, what’s wrong with the way
I drew this atom?
The nucleus is
far too large.
Let’s shrink it.
Is that
small
enough?
Okay.
Let’s
shrink it
again,
then.
Is that small enough for you?
Let’s shrink it again,
then.
Okay. Is
THAT
small
enough?
Why not?
Yep. If you
can see it, I
drew it too
big.
An atom may be
tiny, but it’s
gigantic compared
to the nucleus in
its center.
That’s pretty
strange,
considering that
the nucleus is
where over 99%
of the atom’s
mass is.
Atoms are made
mostly of . . .
Is that small enough for you?
Let’s shrink it again,
then.
Okay. Is
THAT
small
enough?
Why not?
Yep. If you
can see it, I
drew it too
big.
An atom may be
tiny, but it’s
gigantic compared
to the nucleus in
its center.
That’s pretty
strange,
considering that
the nucleus is
where over 99%
of the atom’s
mass is.
Atoms are made
mostly of . . .
And you’re made
of atoms, so . . .
Hey, Mr.
Barnes! I
got a
question!
. . . YOU’RE made
mostly of empty
space.
If I’m made
mostly of
empty
space,
And you’re
made mostly
of empty
space . . .
How come it
hurts so bad
when I kick
you in the
nuts?
Since we’re made mostly of empty space, you’d think
we’d just pass through each other like ghosts.
Instead, we bounce off of each other like billiard balls.
Why is that?
Ask me again
when we’ve
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!
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.
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 they’re
the parts that come closest together. The electrons are
the ambassdors of an atom.
Let’s forget about the atoms and just focus on the
electrons.
Yes we
do,
You’re
gonna
I don’t care if
and you
hear
fromjust
my
you’re sorry.
hurt
mine!
lawyer!
An electron in my foot
An electron in the wall
How do electrons feel about each other?
They’re both negatively-charged, so . . .
They hate each other. Well, okay, they repel each other.
Electrons don’t really have feelings.
So, anyway, electrons push each other away. They feel an
“electrostatic repulsion” for each other.
An electron in my foot
An electron in the wall
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.
An electron in my foot
An electron in the wall
Charge on the
Charge
first object
on the other object
There’s an equation
that predicts the
electrical force
kQ1Q2
between two charged
Fe =
R2
objects. It looks a lot
like Newton’s law of
Electrostatic Distance between
universal gravitiation.
Force
the two objects
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
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
If you make a graph of force versus distance . . .
It’s a downward-swooping curve.
Force (Fe)
An electron in my foot
An electron in the wall
kQ1Q2
Fe =
R2
Distance (R)
The closer the two electrons get . . .
the stronger the repulsive force between them gets.
Force (Fe)
An electron in my foot
An electron in the wall
kQ1Q2
Fe =
R2
Distance (R)
Let’s imagine the electrons getting as close as possible,
close enough to touch.
What’s the distance between two touching objects?
If two objects are touching, there is no longer any distance
between them.
An electron in my foot
In other words, if two
objects are touching, R = 0.
If the number on the bottom
of a fraction equals zero,
what is the value of the
fraction?
An electron in the wall
kQ1Q2
=
Fe =
R2
So, to get my atoms to get close enough to touch the wall’s
atoms, I have to exert an infinite amount of force in order to
overcome the electrostatic repulsion between my electrons
and its electrons.
I’m 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
wall’s atoms before they bounce back.
Well, that was a fun little
mental tangent, but let’s get
back on track and see if
we’ve lived up to our
SWBAT’s for this lesson . . .
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.
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 don’t
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 atom’s 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.
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, positivelycharged particle in the center of an atom. He called it the
“nucleus”.
TPS2: How did Rutherford’s 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.
Don’t move on to the atom-drawing activity until you’ve tried
Mr. Barnes’ atom rules determination activity.
Click the green rectangle
to get the worksheet 
http://www.hhscougars.org/ourpages/auto/2009/9/17/5046529
1/atom%20rules%20determination%20activity%20worksheet
%20DRB.pdf
Click the orange
rectangle to browse the
power point 
http://www.hhscougars.org/ourpages/auto/2009/4/24/3851344
9/atom%20rules%20determination%20activity%20DRB.ppt
. . . draw atoms correctly.
“SWBAT = “Students will be able to”
neutral, so #
Li
3
=#
3
3
Li
7S
-3
4
6.94
S = “Sigma”
Sigma is a
symbol used in
math & science.
It means “sum”
mass # = # protons + # neutrons
or “total”.
# neutrons = mass # - atomic #
neutral, so #
Li
3
=#
3
3
Li
7S
-3
4
6.94
Which two particles are the heaviest?
Where is almost all the mass located?
Materials reminder:
Got graph paper?
User name = hwbrainpop
Password = cougar1
View the “Atoms” and “Atomic Model” cartoons once you’ve
logged in.
NOTE: The student account can only be used during the hours of
8AM – 4PM.
neutral, so #
2
H
1
H
2S
-1
1
1.01
1
=#
1
2 missing
2+
Be
4
Be
9S
-4
5
9.01
, so 4 – 2 =
4
2
2 extra
2-
O
8
O
16S
-8
8
16.00
, so 8 + 2 = 10
8
3 extra
13
C
3-
6
C
13S
-6
7
12.01
, so 6 + 3 = 9
6
It ain’t over til the lady with the shoe on her head says it’s over.
It’s over.
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.