DAY 4
CHEMISTRY SUMMER SCIENCE INSTITUTE
ATOMS: HOW ARE THEY PUT TOGETHER?
This activity concerns the nature of atoms. Atoms themselves are too small to see, but we
know a great deal about their structure by the way they behave.
1.
Place opposite ends (poles) of two bars magnets near each other.
What happens?
Place the same ends of two bars magnets near each other.
What happens?
Fill in the missing words:
2.
Opposites
each other;
Likes
each other.
Take a glass (or hard rubber) rod in your hand and bring it near but do not touch a
suspended pith ball.
What happens?
Rub the rod vigorously with a piece of silk (or wool) fabric. Bring the rod near
the suspended pith balls (do not allow them to touch).
What happens?
Are the pith ball and rod opposites or the same?
What must have caused the change in behavior from the first time you brought
them near each other?
Rub the glass rod with the silk again, but this time allow it to touch the pith ball when
bringing them near each other.
What happens?
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CHEMISTRY SUMMER SCIENCE INSTITUTE
Are the pith ball and glass rod opposites or the same?
What must have caused the change in behavior from the previous try?
3.
Using a quarter, trace 8 circles on a heavy piece of paper. Use a dime and trace 8
more circles. Cut out these circles and draw a big plus sign in the middle of each of
the larger ones and a big minus sign in the middle of the smaller ones.
The +’s represent positively charged particles (protons). You can think of them as
one kind of pole in the magnet. The –‘s represent negatively charged particles
(electrons) or the opposite pole in a magnet. Assume that the different sizes do not
affect the strength of the charge.
Line up all 8 “+” charges in a row, and place all 8 “-” charges in a row under them.
Draw a picture of them here.
If you consider that all the +’s and –‘s are sub-particles, and that collected together
they make one “particle,” what charge would the whole particle have?
Place 8 “+” charges in a row and only place all 5 “-” charges in a row under them.
If you consider these 13 charged sub-particles make up a “particle,” what overall
charge would the “particle” have?
Place 6 “+” charges in a row, but place 8 “-” charges in a row under them. If you
consider these 14 charged sub-particles together, what overall charge would the big
“particle” have?
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DAY 4
CHEMISTRY SUMMER SCIENCE INSTITUTE
4.
Take one of the “+” charged particles and tape it to a “-” charged particle.
What charge does this new sub-particle have?
.
We will call this new sub-particle a neutron.
Make one more neutron by taping a “+” and “-” particle together.
5.
Take your 2 neutrons and 6 “+” and 6 “-” and arrange them randomly in a closely
packed circle making a new round particle. Draw a picture of this round particle.
What overall charge will this new circular particle have?
Imagine that the piece of silk rubbed against this particle touching the outer edges.
Looking at your round particle, which charged sub-particles might be removed or
rubbed off?
______
It is known that the glass rod gets positively charged when rubbed with the silk.
Which type of the sub-particles would have to be removed in order for the remaining
particle to be positively charged?
_________________________
Rearrange your circle of particles so that only the correct kind of sub-particle is on
the outside edges of the large particle. Draw a picture of what you have arranged.
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DAY 4
CHEMISTRY SUMMER SCIENCE INSTITUTE
Back in the early 1900’s a scientist named Rutherford shot some alpha particles
(something like atomic bullets) into some very thin pieces of gold. He thought that
atoms were similar to the circular particles that you have drawn and that the bullets
would all interact with all the gold atoms in about the same way. But what he found
was that most of the bullets went straight through, although some of them were bent
as though they had hit something hard. He theorized that some of the sub-atomic
particles were clustered in the center of the atom and there was space between this
heavy central core and the rest of the sub-particles which must have been on the
outside. The bullets were bent when they hit this heavy middle part of the gold
atoms, but went straight through the empty space or the more spread out other subparticles around the dense atomic core.
Rearrange your sub-particles to conform to Rutherford’s theory of atomic structure,
so that some of the particles are in the middle close to one another and the other kind
of sub-particle (remember which charge has to be on the outside) are outside this
middle portion with space in between the middle and outside sections.
Draw a picture of this atomic model:
What is the overall charge on your “atom?”
_____
Why does it have this charge?
__________________________________________________________________
Are there any questions you would now like to ask?
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CHEMISTRY SUMMER SCIENCE INSTITUTE
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DAY 4
CHEMISTRY SUMMER SCIENCE INSTITUTE
ATOMS: HOW ARE THEY ARRANGED?
The Periodic Table contains all the elements known arranged based on certain properties.
Let’s examine one element box on the Periodic Table.
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The large letter is the SYMBOL that represents one atom of the element
carbon.
C
The “6” above the symbol is the ATOMIC NUMBER. It tell us that the
carbon atoms has six protons in the nucleus and six electrons outside the
nucleus. The atomic number is very specific – no element, other
than C has atomic number 6.
12.011
Is the carbon atom positively charged, negativity charged, or neutral? Explain.
Use the Periodic Table at the end of this activity to help answer the questions that follow.
How many protons are in one atom of potassium (K)?
platinum (PT)
silver (Ag)
How many electrons are in one atom of bromine (Br)?
gold (Au)
radon (Rn)
The other larger number below the symbol is the ATOMIC MASS. Mass refers to the bulk
of an object. Since atoms are so small, it was decided to select an atom of carbon as the
standard for atomic mass. The bulk of all other atoms are compared to C designated as
having a mass of 12 atomic mass units (a.m.u.). Therefore, the average atom of Mg, with
atomic mass of 24.305 a.m.u., is about twice as “bulky” or massive as carbon.
Which element is closest to having 3 times the mass of C?
There is a value called ATOMIC MASS NUMBER which is not on the Periodic Table.
This number tells the number of protons plus the number of neutrons in the nucleus.
If you see a symbol written this way, 126C , with the upper number written as a whole number,
than this 12 is the atomic mass number.
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DAY 4
CHEMISTRY SUMMER SCIENCE INSTITUTE
This carbon atom has 6 protons, 6 electrons, and 6 neutrons.
12 (p + n) – 6 (p) = 6 neutrons.
Be = p = 4, e = 4, n = 5
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You try this one:
F
19
9
p = __, e = __, n = __
Now atoms of 146C are known to exist. In this case, p = 6, e = 6, n = 8
Most atoms of carbon are 126C or C-12, (the standard for atomic mass), but a small proportion
of natural carbon is the ISOTOPE C-14 ( 146C ) that has an extra 2 neutrons in the nucleus. It
is still carbon (the fact that it has 6 protons determines that), but it is a more massive atom.
The atomic masses on the Periodic Table are actually average masses of all the natural
isotopes of that element. This ia another reason why the masses on the table are not whole
numbers. Complete the following table.
Element
Copper
Sodium
Iron
Symbol
Atomic
Mass
Cu
Na
Atomic
Mass
Number
#p
64
29
22.98977
#e
#n
12
Fe
30
Silicon
28
I
14
127
Are the elements arranged on the Periodic Table by atomic number or atomic mass?
Which element appears on the Periodic Table more than once?
Which element has no neutrons?
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CHEMISTRY SUMMER SCIENCE INSTITUTE
Which element has 114 neutrons?
Do you know which elements are liquids?
Do you know which elements are gases?
Which element is a bright yellow solid?
Which element will melt in your hand?
Which element was once so rare that chunk of it was once on display in the Smithsonian, but
is now used to line baking plans and wrap sandwiches?
Do you know the 2 elements discovered by Marie Curie?
Do you know the name of the latest element to be named in 1997?
HINT: Symbol = Mt atomic no. 109
What is name of element No?
HINT: He invented dynamite.
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CHEMISTRY SUMMER SCIENCE INSTITUTE
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DAY 4
CHEMISTRY SUMMER SCIENCE INSTITUTE
WHAT’S IN A FLAME?
Take a good look at the bottles of liquid on the table.
What color are these liquids?
1. ____________________
3. __________________
2. ___________________
4. __________________
5. __________________
If the labels fell off these liquids, do you think you could tell which was which just by
looking at the liquids? Why or why not?
Light the Bunsen burner. Holding one of the squeeze bottles parallel to the flame, gently
squeeze some solution into the flame. Repeat as needed until you can accurately describe the
color and record the color you see below. Do the same thing for the other four solutions. Be
sure to wipe the area around the Bunsen burner with water when you are done.
What colors do you see in the flame?
1. ____________________
3. ____________________
2. ____________________
4. ____________________
5. ____________________
Now if the labels fell off the bottles, what could you do to tell which bottle was which?
If two solutions were mixed together could you identify the two different components? Why
or why not?
_________________________________________________________________________
Are there any questions you would like to ask?
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DAY 4
CHEMISTRY SUMMER SCIENCE INSTITUTE
GASLIGHTS – ONE COLOR OR MANY?
When energy is put into atoms (by adding electricity or heating them) the energy can be
temporarily absorbed. It is then released in the form of light (another form of energy). We
perceive light as different colors.
1. Locate the brightly colored glasses on the table and put them on. Look at a source of
white light.
What do you see? ________________________________________________________
Why? _________________________________________________________________
White light is really composed of all colors. The colors in white light can be separated by
passing the light through a prism or a diffraction grating (the lenses of the glasses).
Let’s explore some elements by passing electricity through them. We will do this using
discharge tubes containing different elements and high voltage power sources (the black
boxes).
BE CAREFUL OF THE EQUIPMENT USED IN THIS SECTION. THE BULBS ARE VERY
FRAGILE AND ARE ENERGIZED BY A HIGH VOLTAGE SOURCE. DO NOT TOUCH
THE TUBES OR THE POWER SUPPLY.
2. Look at the power supply containing the hydrogen tube with your glasses on. How is it
different than the other light source?
Record the colors as you see them. Use colored pencils to draw the pattern in the data
chart on the next page
3. Now look at the tube containing the helium in another power supply. Is it the same or
different? How?
Record the pattern you see.
4. Repeat the same process with the tubes containing mercury and neon.
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DAY 4
CHEMISTRY SUMMER SCIENCE INSTITUTE
ELEMENT
LINE SPECTRUM
HYDROGEN
HELIUM
MERCURY
NEON
The colors that you see being emitted from these discharge tubes is coming from the atoms of
the different gases in the tubes. Different kinds of atoms emit different colors. Each of these
lights is actually composed of many colors. By looking through a portable spectroscope,
your diffraction glasses, you can separate and see the component “spectral lines” of color.
5. Try to figure out what element is in Tube X. Repeat the procedure you did before using
the tube containing Elements X. This tube contains one of the elements you saw before.
ELEMENT X
What is Element X? ____________________________________________
Explain why you decided this.
If you allowed the light from a distant star to pass through the spectroscope, what
information could you obtain about the star?
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DAY 4
CHEMISTRY SUMMER SCIENCE INSTITUTE
ATOMS: MAKING A MODEL
1. Using gum drops (to represent sub-atomic particles), coffee stirrers (to mount electrons)
and Elmer’s Glue, put together a model of one atom of nitrogen.
N
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2. If 3 extra electrons were added to your nitrogen atom:
Would it still be the element nitrogen?
Explain
Would it still be an atom?
3. Try to think like an elementary school student! If you showed them the model of the
nitrogen atom that you have just made, what ideas about atoms might they derive from
this model? Make a list.
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