Download Atoms and nukes packet 2016

(Formative) Chem Activity: Atoms and Isotopes Name _____________________________
page 1
You can find these animations at https://phet.colorado.edu The HTML5 versions will run on your
phone or tablet, along with the computer.
This activity will help you with Atoms and Isotopes. Open the HTML5 animation file
isotopes-and-atomic-mass_en.html from the Dropbox, ChemL3 labs, atoms and nukes folder. Let’s
build some atoms! These animations are pretty self explanatory and intuitive. If you really mess up
you can always click the orange circle, or the eraser button to start over.
1. The Atomic Number is the number of ______________ in the nucleus of an atom (Big blue number
on your Periodic Table).
!
The Mass Number is the number of _____________ + ________________.
Isotopes are atoms with the same number of ____________ but different number of ___________ or
Same ______________, Different _______________, or the same_____________, different __________
Since Isotopes are the same __________, they act chemically alike, but very differently in nuclear changes.
Some atoms are stable and occur in nature, and some are Unstable, or Radioactive. The “Abundance”
in this app is the % of that Isotope as it occurs in nature.
2.! Start on the Make Isotopes Tab. Make sure the Symbol and Abundance in Nature boxes are
open. (click the green +sign). To fill in this Table: Click on the Element in the Periodic Table.
Drag neutrons in or out of the nucleus to make each atom.
Protons Neutrons % Abund or
Symbol Atomic Mass
Protons Neutrons % Abund or Symbol Atomic Mass
“Unstable”
of Atom Number Number
“Unstable” of Atom Number Number
1H
1
1
1
0
99.9%
2H
Unstable
3H
3He
C
13
C
14
N
13
2
3
2
4
15O
2
5
16O
8
17O
4
9
18O
4
10
18F
14
7
4
19
9
B
5
20
9
B
6
8Be
9B
5
20Ne
11C
11
10
11
C
12
10
12
3. The Atomic Mass is the exact mass of one atom in atomic mass units. How is this
different from Mass number? You can switch between Mass Number and Atomic Mass
using the buttons on the Balance. Make the Atoms and fill in the following Table.
Remember that Counted numbers have Unlimited sig figs.
Atom
9Be
Mass
Number
# sig figs Atomic Mass
# sig
figs
page 2
(Form)
Atomic Mass rounded
to 3 sig figs
unlim
10B
11B
19F
Notice that the Atomic Mass is not exactly a whole number, but is close to a whole number. (The
reason for this has to do with matter energy changes and is beyond the scope of this course).
Since we only need 3 sig figs for most of the calculations we do this year in Chemistry, we will
round the Atomic Mass to 3 sig figs, (which is basically the same as the Mass Number).
Now use your result from the first Table to answer the following questions.
4. Write an atom that has the same number of protons as 10B ___________ as 20Ne _____________
The same neutrons as 9Be _______ as 12C _______. Same Mass number as 11C ______, as 18O ______
Same Atomic Number as 2H ________, as 17O ________. An isotope of Helium ________, of F _______
5. What is the difference between 12C and 14C? What is alike about them?
6. What is the difference between 14C and 14N? What is alike about them?
7. Would 16O act chemically like 18O? Explain.
8. Would 14C act chemically like 14N? Explain.
9. Does 12C act like 14C in terms of nuclear changes? Explain.
10. What seems to make an atom “unstable” (in terms of number of Protons and neutrons).
11. Do all elements have more than one stable isotope? Give example(s).
12. Are all the isotopes of an element equally abundant? Give example(s).
(Summative) Chem Activity: Average Atomic Mass and Isotopes!
Page 3
An important value in Chemistry is the Average Atomic Mass (or Atomic Weight) of an Element. This is
the Average Mass of the element as it occurs in nature, or the Weighted Average of the masses of
these isotopes in nature. On your Periodic Table, this is the little red number above the symbol
Open the HTML5 animation file : isotopes-and-atomic-mass_en.html
Click on the Mixures Button. Click on the “My mix” button under Isotope Mixture. Dragging and
dropping the atoms from the pans into the black space will make different mixtures of isotopes.
Clicking on the slider (lower right of black space) changes to sliders to add atoms. Open the %
Composition and Average Atomic Mass Boxes on the right (click red/green, -/+ buttons).
1. What is the Average Atomic Mass if an element has only one stable isotope in Nature? Click on
Berylium (Be) in the Periodic Table. What is the Stable Isotope of Be? _____________
!
Drag atoms into the black space. What is the Average Atomic Mass of Be? ___________ round
this to 3 sig figs._____________. Look this number up on your Periodic Table _____________
2. There is only one stable isotope of Fluorine, 19F. What do you predict to be the Average Atomic
Mass of Fluorine? _____________________. To 3 sig figs? ___________________
!
Click on F to confirm your prediction, or check your Periodic Table.
3. So Write this General Rule: If there is only one stable isotope of an element, its Average Atomic
mass is :
!
And the reason for this is:
But we’ve seen that many elements have more than one stable isotope, and that not all the isotopes of an
element are equally abundant. How does this affect the Average Atomic Mass?
4. Click on “My Mix.” Click on B (Boron) in the Periodic Table. It has 2 stable isotopes:
______________ and _____________
5. Mix equal numbers of these Isotopes in the black space (drag and drop or use the sliders). What is
the calculated Avg At. Mass? ____________ (to 3 sig figs) Explain this answer.
6. Add more 10B. What happens to the Avg. At. Mass? Why does this happen?
7. Now remove some 10B and add more 11B. What happens to the Avg. At. Mass? Why does this
happen?
8. The actual Avg. At. Mass of Boron is 10.8 amu (rounded to 3 sig figs). !
! Do you predict there is more 10B or 11B in Nature? Why? !
Page 4
(Summative)
9. Try to adjust “My mix” to get this Average Mass, 10.8 amu.
!
How many 10B atoms _______________ and 11B atoms ___________ are in this mix?
!
What is the % 10B ________________ and % 11B ______________ that gives you this Average?
! Click on “Nature’s Mix” to confirm your predictions.
***10. This Formula is used to calculate the Average Atomic Mass (a weighted average) (also called
Atomic Weight): Write this formula on your Handout!!
Average At. Mass = Mass number (% abundance) + Mass num (% abund) + ...
!
(for all isotopes)
Using this formula, Show work to confirm this for Boron. Express your Avg. At. Mass to 3 sig figs.
11. Chlorine is 75.8 % 35Cl and 24.2 % 37Cl. Would you predict the Avg. At. Mass for Chlorine is closer
to 35, 36 or 37? Why?
12. Show work to calculate the Avg At. Mass for Chlorine. Express your answer to 3 sig figs. Click
on Nature’s mix (or use your Periodic Table) to confirm your answer.
13. Elements that have all Radioactive isotopes don’t really have an “average” in nature. Instead, on
your Periodic Table, the most stable isotope is listed in Parentheses. Look up Po ____________ and
At ____________ on your Per Table for examples.
14. On your Periodic Table, look up the atomic weights (to 3 sig figs) for Helium ___________ and
Oxygen _________. What Isotope do you think is its most abundant? He _________ O _________
! You can confirm your predictions with Nature’s Mix.
15. Nitrogen is about 99.5 % 14N. What do you think is the approximate Average Atomic Mass for N?
Why?
16. Magnesium has an Average Atomic Mass of 24.3 amu. Do you think Mg has only one stable
isotope, or more than one stable isotope. Why do you think so? You can confirm your prediction
with Nature’s mix.
(Formative)
Page 5
Nuclear Changes and Radioactive Decay Worksheet (see p. 118-120, Sam. prob 5-4)
Use your notes to predict the products in these nuclear equations.
1. Complete the equation for the α (alpha) decay of the following atoms. (p. 843)
210Bi ---->
83
143Sm
62
---->
2. Complete the equation for the β- (beta) decay of the following atoms. (p. 843)
234Th ---->
90
3.!
!
60Co
---->
27
Complete the following nuclear reactions. Then state the type of nuclear reaction
(α decay, β- decay, fission, fusion, transmutation): (p. 843, 850-856) (ans below)
a. 90Sr ---> 0e + ______
38
-1
b. 235U ---> 4He + ______
92
2
c. 9Be + 4He ---->
______
4
2
____________________
____________________
+ 1n
0
____________________
d. 235U +1n --> 137Cs + ______ + 3 1n 92 0
55
0
e. 2H + 3H ----> ______ + 1n
1
1
0
____________________
f. 239Pu + 2 1n ---> 0e + ______
94
0
-1
g. 131I ---> 131Xe +
______
53
54
h. 14N + 4He --> ______ + 1H 7
2
1
i. 239Pu + 1n --> 146Ba + ______ + 4 1n 94
0
56
0
j. 56Fe + 2H --> ______ + 4He 26
1
2
____________________
____________________
____________________
____________________
____________________
Transmutation!
4. What's the difference between the nuclear reactions that take place in the sun and those in a
nuclear power plant?
(1a. 206Tl; b. 139Nd; 2a. 234Pa; b. 60Ni; 3a. 90Y, β-; b. 231Th, α; c. 12C, fusion; d. 96Rb, fission; e. 4He,
fusion; f. 241Am, transmutation; g. β- ; h. 17O, fusion; i. 90Sr, fission; j. 54Mn)
(Summative) Chemistry Activity: Determine your Radiation Dose !
Page 6
! In this activity, we’ll find out about some Radiation we’re exposed to in the course of a year. With
Chrome, open the file “radiationcalculator.swf” in the Dropbox, ChemL3 labs, atoms and nukes
folder of Dropbox. Click through the Interactive to answer these questions. It will calculate your
Annual radiation dose as you answer the on screen questions.
You can also find this file at : http://www.omsi.edu/exhibits/hanford/radiationquiz.htm
1. Why does altitude matter? (Click on the text box on each screen to get the answers).
2. In “Where do you live?” What about New Hampshire would make it high in Radon risk?
3. Why does flying in an airplane increase your radiation dose?
4. What is the purpose of Pu in a pacemaker?
5. What radioactive isotope is in a smoke detector? ________
6. How much radiation comes from smoking a pack of cigarettes a day? _____________ What
isotopes produce this radiation? _____________
7. What isotope is found in glow in the dark watch dials? __________________
8. What are the two main radioactive isotopes found inside your body (Sharing a bed)? ____________
9. What is the national average radiation dose? ________________
10. What is the average extra dose received by a Hanford Radiation worker? _______
11. What is the maximum legal limit by a Radiation worker? ___________
12. The last slide of the interactive indicates your annual radiation dose. Click Restart and calculate
the other partner’s dose, too. So what is your calculated yearly radiation dose?
Name ___________________ dose_________!
Name __________________ dose___________
13. Is either partner’s dose higher than the national average? What contributed to it being this high?
14. Radon gas is about 200 mrem of your calculated dose. What percent is that of your total?
! 200 mrem x 100 =
! your dose
15. Living within 50 miles of a nuclear power plant (like Seabrook) adds 0.009 mrem per.
Living within 50 miles of a coal fired power plant (like Bow) adds 0.03 mrem per year. Are these
extra doses significant? Explain.
16. Why do you think Radioactive isotopes of Carbon are especially harmful to living creatures?
(Formative) Activity: Half lives Radioactive decay can be used as a clock to estimate !
page 7
! the age of certain objects. Open the java app file radioactive-dating-game_en.jar
Click on the Tab Decay Rates. Choose 14C. Use the Slider button on the bucket to add Radioactive 14C
atoms (red) to the workspace. These atoms will then decay to 14N (blue). The graph at the bottom
shows the percentage of these atoms in the resulting mixture. Clicking the Reset All Nuclei button
will restart the decay. The half life of 14C is about 5700 years.
1. Slide the slider a little to the right. Watch the decay. Click Reset All nuclei, and watch again.
Repeat a few times. Slide the slider more to the right and start over. Repeat. Slide the slider a few
more times and repeat. Experiment and see if the pattern changes.
! After 1 half life, approximately what % of 14C remains __________ After 2 half lives ________
After 3 half lives ________
!
!
What % do you think would be left after 4 Half lives? ___________ 5 half lives?___________
Why do you think so?
!
Do these percentages change depending on how many atoms you start with? Yes or No
2. Repeat step 1 with 238U (half life 4.5 x 109 years, or 4.5 billion years.) After 1 half life, approximately
what % of 238U remains ______ After 2 half lives _____ After 3 half lives ______
!
Are these percentages the same as for 14C? In other words, do the percentage change depending
on how long the half life is?
3. a. How long is 2 half lives of 14C? ___________ What % of 14C would remain? _________
!
If you start with 50 grams of 14C, how many grams remain after 2 half lives? ___________
!
b. How many half lives of 14C are 11400 years? ______ What % of 14C would remain? _______ If
you start with 300 g of 14C, how much is left after 11400 years?______________
!
c. You start with 60 mg of 14C. Some time later you only have 30 mg of 14C. What % is this?
________ How many half lives have elapsed? ________ how many years is this? ___________
4. a. How long is 2 half lives of 238U? ___________
What % of 238U would remain? _______
!
If you start with 50 grams of 238U, how much is left after 2 half lives? ___________
!
b. How many half lives of 238U are 9.0 billion years? _______ What % would remain? ______
!
If you start with 300 g of 238U, how much is left after 9.0 billion years?_______________
!
c. You start with 60 mg of 238U. Some time later you only have 30 mg of 238U. What % is this?
_____ How many half lives have elapsed? ________ how many years is this? ___________
5. If the same % of any radioactive isotope remains, would this be the the same number of half lives?
Yes or No Would it be the same amount of time? Yes or No Would the change in mass be the same?
Yes or No
(Formative) ! Half-lives Practice Problems: Page 8
(see p. 847-850, Sample prob 28-1, half lives are on your handout)
1. Compare the half life of a radioactive isotope to a single elimination sports tournament.
2. Biologists study how plants use fertilizers using 32P. Look up the half life of 32P ___________ How
many half lives is 57.2 days? _____ So what % of 32P would remain after 57.2 days? ______
! How much of a 60.0 mg sample of 32P would remain after 57.2 days? ___________
3. How much of a 12.0 mg sample of 226Ra will be left in 3200 years (3.20 x 103 years)?
(3 mg)
4. The government has 500 g of 239Pu to store somewhere safe from dismantling a nuclear bomb.
How much of the 239Pu would be left in 72300 (7.23 x104) years? !
(62.5 g)
5.
131I
can be used to diagnose thyroid disease. Look up the half life of 131I _________ Suppose you
are dosed with 45.0 mg of 131I. You can go back to school when this decays to 5.62 mg 131I. What
percentage of the original would this be? ___________ How many half lives would this
correspond to? _________ How many days is this? ___________
6. How long will it take for a 300 mg sample of
223Fr
to decay to 37.5 mg of
223Fr?
!
(65.4 min)
7. How long will it take for a 100 mg sample of 239Pu to decay to 25 mg of 239Pu? (4.82 x 104 years)
8. In 1986, suppose a bomb test produced 90Sr as fallout. In 2015, 375 g of 90Sr remains from this test.
How much 90Sr was produced back in 1986? !
(750 g)
9. A 20 g sample of Thorium-234 is placed in a sealed container. In 75 days only 2.5 g of Thorium-234
is left. Determine the half-life of thorium-234 using this information.
(25 days)
(2. 14.3 d, 4, 6.25%, 3.75 mg; 5. 8.04 d, 12.5 %, 3, 24.1 d)
(Summative) Activity: How Old is that Rock?!
Page 9
Indiana Jones and Nicholas Cage are searching for buried treasures again. They think they may find
something in your backyard! They’re searching for 30 million year old fish fossils, 2000 year old
cups and billion year old rocks! Radioactive dating will help us estimate the age of some objects.
But objects of different ages need isotopes with different length half lives. After about 6 half lives,
pretty much all of the original is decayed, and the technique isn’t useful. Or, at the very start, not
enough has decayed to give an accurate result. Can you select the correct isotope to use to date
some bones and rocks and become famous?
Open the java app file radioactive-dating-game_en.jar (Dropbox, ChemL3 labs, atoms and nukes...)
1. Click on the Measurement Tab and try out using the Probe. Does 14 C work with everything? How
about 238U? For the Tree, notice the time is elapsed from the time the tree dies (and stops taking in
14C from the atmosphere), not when it starts growing.
2. Click on the Dating Game Tab.
! Drag the probe to various objects until you see a “Estimate the age of ...” box. Look at the graph at
the top of the page and slide the green double arrow in the graph until the % matches what you
see. Since it’s an estimate, you only need 3 sig figs in your time, and there is a little leeway in the
correct years. Type your estimated time in the box and click Check Estimate. Try again with the
other objects on the Surface and in the Top layer.
Object
Isotope used % remain
age (yrs)
Dead Tree
House
Leave the Green Happy boxes open!
Your teacher will sign the back of
your paper when you’re all done!!
Distant Tree
Tree
Animal skull
Human Skull
Wooden Cup
Bone
Fish bones
Rock 3
Rock 4
Rock 5
3. Why did you use 14C to estimate the age of some objects?
4. Why did you use 238U to estimate the age of some objects?
The second and third layer (strata)
are a little trickier. Skip them and go
down to the lowest layer. We’ll do
them on the back.
5. Objects in Layer 2, 3, and 4 !
(Summative) ! Page 10
need to use “custom” half
Object
Isotope Length of
%
age (years)
lives. Try it to see what
used
Half life
remain
length half life you need for
Fish bones custom
each.
Smaller
custom
human
skull
6. Two different custom
custom
isotopes should both work Dinosaur
skull
for the Fish fossil.
238U and a custom isotope
Rock 1
custom
should work for Rock 2. Try Fish fossil custom
with both isotopes that work.
Fish fossil custom
Record your results in the
Trilobyte
custom
Data Table.
Rock 2
custom
When you’re all done, leave
238U
Rock 2
the green happy boxes
open and have your Teacher sign here _________________________
7. Nicholas Cage thinks the smaller human skull dates from the Revolutionary War. Is this possible?
Why or why not?
8. Indiana Jones says the Wooden cup is from some Native Americans. Is this possible? Why or why
not?
9. A newspaper article says a rock was dated to 5 million years using radioactive 14C dating. Why is
this wrong?
10. Look up the half life for Tritium, 3H,_________. Suppose 200 g of 3H was introduced into the
atmosphere during Hydrogen Bomb testing in the 1960’s. How many half lives of 3H are
approximately 49 years? _______ What % of the 3H remains? ________ How many grams of 3H is
left? ________
11. Look up the half life for 90Sr. ___________ An Atom Bomb test released 400 g of 90Sr. Some time
later there is only 100 g of 90Sr. What % of 90Sr remains? _________ How many half lives have
elapsed? _____________ How many years is this? _________________
(Formative) Review sheet: Unit 3
page 11
1. Dalton's atomic theory says that all matter is made up of atoms and a) atoms are _____________ b)
all atoms of the same element are _______________ c) atoms combine in __________________
ratios and d) atoms are not _______________, only rearranged in chemical reactions.
2. Current atomic theory does not agree with a b c d above. (circle)
3. Given: 2H, 3H, 4He, 39Ar, 40K, 39K, 40Ca, 235U, 238Np: Which is (or has):
!
a. an isotope of potassium _________!
c. the same number of neutrons as 3He ______!
!
b. the same number of protons as 238U _______!
d. the same mass number as 40Ar ______
4. Name a radioisotope used in the following: a. cancer radiation therapy__________
!
b. radioactive dating _________! c. diagnosing disease _________!
5. Look up the type of decay on your handout and give the equation for its decay.
! a. 72Ga -----> !
b. 232Th -----> ! !
6. Complete the following table
Atomic!
Mass!
number of!
number!
number!
protons!
______!
40!
______!
______!
______!
_______!
______!
______!
_______!
______!
______!
_______!
number of!
neutrons!
22!
16!
_______!
_______!
number of!
electrons!
_______!
15!
_______!
_______!
Name of!
symbol of
atom!
atom
__________!
_______
__________!
_______
Carbon-14!
_______
59Co
___________!
7. Gallium exists in nature as two different isotopes, 69Ga and 71Ga. Which one is more abundant?
Why do you think so? (Hint: Check your Periodic Table)
!
b. 36.2 % of the Gallium is 71Ga. Show work to calculate the atomic weight of Gallium.
8. A hospital has e a 20.0 mg sample of 60Co for radiation therapy. Half life = ________ When the
60Co decays to 5.0 mg it’s no longer useful. What % is this? _________ How many half lives?
______ How long is this ?________________ !
(10.54 yrs)
9. You get 2.0 mg of 257Fm from a chemical supply house. Half life = _______ How many half lives is
300 days? ______ What % remains? __________ How many mg of 257Fm would remain? ______
!
(0.25 mg)
10. You receive 0.25 mrem of radiation from a short airplane flight. Is this significant? Explain.
11. Some 223Fr was produced in the Chernobyl accident 26 years ago. Is this 223Fr still dangerous?
Explain.
(2. a&b; 3a. 40K, 39K; b. 235U; c. 2H; d. 40K, 40Ca; 4a. 60Co; b. 14C, 238U; c. 131I; 5a. beta; b. alpha)
Page 12
Formative
Crossword Puzzle:
Atoms and Nuclear Chemistry
ACROSS CLUES
2. The most common cause of man-made
radiation exposure is medical _________.
4. The type of nuclear change in the sun.
7. Atoms of the same element with different
mass numbers.
9. Mass number 22; 12 neutrons.
12. The part of the atom containing negatively
charged particles. (2 wds)
14. Isotopes act alike in ______ changes.
16. The most penetrating type of radiation.
19. The element with 55 protons.
21. Element with atomic number 50.
22. Isotopes act very differently in ______
changes.
23. The electron cloud contains most of the
______ of the atom.
24. Has an isotope with mass number 14 that is
used for radioactive dating.
26. A helium nucleus is a(n) ______ particle.
DOWN CLUES
1. The time for one half of a sample of radioactive
atoms to decay.
3. A radioactive gas that can be dangerous in
basements.
4. A nucleus is split into two large pieces.
5. The element with atomic weight 55.845 amu
6. The average mass of an element as it occurs in
nature(2 wds)
8. The releases of particles and energy from an
unstable nucleus is ___ decay.
10. The _____ of oxygen is 8 (2 wds).
11. A neutral subatomic particle.
12. The smallest major subatomic particle.
13. Element with 82 electrons.
15. Plutonium is a(n) _______ element.
17. In “Carbon-12,” 12 is the ______. (2 wds)
18. The ____ contains most of the mass of the atom.
20. The positive particle found in the nucleus.
25. Type of decay rubidium–87 undergoes.