
Half-Life Review Lesson
Presentation
•
Physics
•
9th - 12th Grade
•
Medium
Standards-aligned
Christine Ruberti
Used 4+ times
FREE Resource
3 Slides • 8 Questions
1
What is half-life and how is it calculated?

2
It is the time taken for a radioactive isotope to decay to half its original value.
Time can be seconds, minutes, hours, weeks, months or years
It varies depending on the isotope
3
Fill in the Blanks
Half-life is the period of time it takes for an isotope to decay to
Type answer...
4
Multiple Choice
What is an isotope?
one of several forms of the same atoms; same number of protons but have different number of neutrons
a particle that has no charge and is located in the nucleus of an atom.
energy in the form of waves or particles that is emitted from an object and travels through space or air
5
Multiple Choice
Geologist use the time it takes for a radioactive isotope to decay to half its original mass called a___________.
radioactive decay
isotope
half-life
carbon dating
6
Multiple Choice
What is the only difference between two different isotopes of the same element?
Number of neutrons
Number of protons
Number of electrons
Size of atom
7
Radon-222 decays with a half-life of 3.82 days. If an initial sample of the element contains 1000 atoms, how much remains after 15.28 days?
Half-life = 3.82 days
# of half-lives = 15.28/3.82 = 4
1000--> 500 --> 250-->125-->62.5 atoms
62.5 atoms remains after 4 half-lives.
8
Multiple Select
The half-life of strontium-90 is 25 years. How much strontium-90 will remain after 100 years if the initial amount is 4.0 g?
What do we need to know to answer this question? (Check all that applies)
the half-life for the given sample
the number of half-lives passed based on the total time
to multiply by 2
if alpha decay occurs
9
Multiple Choice
If 20 mg of iodine-131 is given to a patient, how much is left after 32 days? The half-life of iodine-131 is 8 days.
32
1.25
10
2.5
10
Multiple Choice
Barium-122 has a half-life of 2 minutes. A fresh sample weighing 80 g was obtained. If it takes 10 minutes to set up an experiment using barium-122, how much barium-122 will be left when the experiment begins?
0.25g
2.5g
25g
80g
11
Multiple Choice
You have 100 grams of radioactive C-14. The half life of C-14 is 5730 years.
How many grams are left after 1 half life?
100g
50g
25g
2g
What is half-life and how is it calculated?

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