Half-Life practice 1 2 What is half-life?

Half-Life practice

1 Create a graph that represents how a radioactive element will decay.

2 What is half-life?

100 90

80

% of original mass remaining

70

60

50

40 30 20

4 Gold-198 has a half life of 2.7 days. Complete the table for an initial sample size of 200 grams.

10

0 1 2 3 4 5 6 7 8 9 10

3 Number of half-lives The half-life of Po-214 is 0.001 seconds. How much of a 10-gram sample is left after 0.003 seconds?

Time Elapsed

0 days 2.7 days

Amount Remaining

200 grams

5 The graph below shows the breakdown of radon-222. 6 How much of a 500g sample of potassium-42 is left after

37.2 hours if the half-life of potassium-42 is 12.4 hours.

7

How much of a 100 gram sample of gold-198 is left after 8.10 days if its half life is 2.7 days?

What is the half-life of Rn-222? ________ What fraction of the original sample will be left after 3 half-lives?____

?The Trendy Science Teacher 2020

8

Time (days)

The table below shows the radioactive decay of a 600 g sample of iodine-125.

Half-lives

% of Parent Isotope Fraction of Parent Mass (g) of Parent

Remaining

Isotope Remaining

Isotope

0

0

100%

1/1

600

60

1

50%

?

300

120

2

25%

?

150

180

3

12.5%

1/8

75

240

4

6.25%

1/16

37.5

300

5

3.125%

1/32

18.75

360

6

1.56%

1/64

9.4

a. What percent of iodine is left after 5 half lives have passed? b. What percent of iodine-125 has decayed if there are 37.5 grams of the original sample left? c. What is the half life of iodine-125? d. What mass of the iodine-125 has decayed after 6 half-lives? e. What fraction of the iodine-125 remains after 300 days have passed? f. How many half lives would have to pass for there to be only 1.2 grams remaining?

9 Create your own half life problem in the space provided below. Then solve.

?The Trendy Science Teacher 2020

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