1. Multiply mass x % for all isotopes.
Abundance of Isotopes
Multiply mass x % for all isotopes.
Add them.
Strontium consists of four isotopes with masses of:
84 (abundance 0.50%),
86 (abundance of 9.9%),
87 (abundance of 7.0%), and
88 (abundance of 82.6%).
Predict the average mass of Strontium. ______
Calculate the atomic mass of strontium.

2. Half-Life 2 Times (Hint: Solve for # h.l. first!! )
1. The half-life of cobalt-60 is 5.26 years. How many half-lives have passed in years? What % of the sample remains?
2 Amounts
(Hint: Solve for # h.l. first!! )
2. A rock that originally had a mass of 1.00 gram of uranium-238 now has only grams. How old is the rock if the half-live of uranium-238 is 4.5 billions of years.
3. How old is an artifact if 6.25% of C-14 remains in the sample and the half-live of carbon-14 is 5730 years?
Find the half-life
(1 h.l. = total time)
total # h.l.
4. All isotopes of technetium are radioactive, but they have widely varying half-lives. If an g sample of technetium-99 decays to g of technetium-99 in 7 hours, what is its half-life?

3. Nuclear Reactions Subatomic nuclear symbols:
___ proton, ___ neutron, ___ electron
Alpha decay (42He, big, slow, stopped by clothes/paper)
Beta decay (0-1e, med, med, stopped by Al foil)
Positron decay (0+1e, med, med, stopped by Al foil)
Gamma decay (00 w/ alpha or beta, small, fast,
NOT a particle..it’s energy! stopped by lead/concrete)
Write the decay equations for:
a. Polonium-210 w/ alpha particle ejected
b. Bromine-85 beta decay w/ gamma emitted
c. Tin-116 positron decay

4. Fusion and Fission Nuclear Fusion 1. What happens to the nucleus?
2. What happens to the energy?
3. Is fusion controllable?
4. Name 2 places where fusion happens.
Nuclear Fission
What happens to the nucleus?
What happens to the energy?
How does a chain reaction work?
Is fission controllable?
Name 2 places where fission happens.
9. How does an atomic bomb incorporate fission AND fusion?