1. Section 3 Uses of Nuclear Chemistry
Chapter 18
Half-Life
The _________ is the time required for half of a sample of a radioactive substance to disintegrate by radioactive decay
The half-life of a radioactive isotope is a ___________ and is not influenced by any external conditions, such as temperature and pressure.
half-life
constant value

2. Radioisotope Half-life Radioisotope Half-life
Section 3 Uses of Nuclear Chemistry
Chapter 18
Half-Life
Radioisotope Half-life Radioisotope Half-life
Bismuth min Polonium sec
Carbon yrs Polonium sec
Chlorine yrs Radium yrs
Cobalt yrs Sodium hrs
Iodine days Strontium yrs
Iron days Uranium mill yrs
Phosphorus days Uranium bill yrs

3. Section 3 Uses of Nuclear Chemistry Chapter 18
Half-Life
Example Problem:
212 Bi b Po
If you start with 200 g, how much is left after min?
Answer:
The half-life of bismuth-212 is ___________.
How much is left after one half-life (60.5 minutes)?
How much is left after 2 half-lives (121 minutes)?
How much is left after 3 half-lives (181.5 minutes)?
60.5 minutes
100 g
50 g
25 g

4. 2 226Ra 88 4 a + 222Rn Section 3 Uses of Nuclear Chemistry Chapter 18
Half-Life
Practice Problem:
Radium-226 undergoes alpha decay.
Write the transmutation equation for this change.
What is the name if the new substance that is produced?
If you start with 4000 g, how much will be left after 6408 years?
Answers:
(A)
(B) Radon-222
226Ra 88
4 a + 2
222Rn 86

5. Half-Life Section 3 Uses of Nuclear Chemistry Chapter 18
Practice Problem (continued):
Radium-226 undergoes alpha decay.
(C) If you start with 4000 g, how much will be left after 6408 years?
Answer:
What is the half-life of Radium-226?
How much is left after 1 half-life?
How much is left after 2 half-lives (3204 years)?
How much is left after 3 half-lives (4806 years)?
How much is left after 4 half-lives (6408 years)?
1602 years
2000 g
1000 g
500 g
250 g

6. -1 7 Half-Life Section 3 Uses of Nuclear Chemistry Chapter 18
Practice Problem:
Carbon-14 undergoes beta decay.
Write the transmutation equation for this change.
What is the name if the new substance that is produced?
If you start with 600 g, how much will be left after 17,790 years?
Answers:
14C 6
0b + -1
14N 7
(A)
(B)
Nitrogen-14

7. Half-Life Section 3 Uses of Nuclear Chemistry Chapter 18
Practice Problem (continued):
Carbon-14 undergoes beta decay.
(C) If you start with 600 g, how much will be left after 17,790 years?
Answer:
What is the half-life of carbon-14?
How much is left after 1 half-life?
How much is left after 2 half-lives (11,860 years)?
How much is left after 3 half-lives (17,790 years)?
5930 years
300 g
150 g
75 g