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Half life

Total questions: 13

Worksheet time: 41mins

Name
Class
Date
1.

What is Half-life?

a)

The amount of time it takes for half the nuclei in a sample of the isotope to become radioactive

b)

The amount of time it takes for half the nucleus of the isotope to decay

c)

The amount of time it takes for half the nuclei in a sample of the isotope to decay

d)

the amount of time it takes for half the number of protons in the nucleus to decay

2.
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?
a)
3.0g
b)
0.25mg
c)
0.3g
d)
0.25g
3.
When nuclei decay, massive amounts of __________ is released.
a)
energy
b)
jello
c)
protons
d)
neutrons
4.
What is the half-life of iodine-131?
a)
32 days
b)
8 days
c)
16 days
d)
24 days
5.
If one-fourth of the carbon-14 is remaining then how many half-lives have passed?
a)
1
b)
2
c)
3
d)
4
6.

Why do some elements have half-lives?

a)

they radioactively decay

b)

half of their atom gets stolen

c)

They are Twizzlers that break in half

7.
After the third half-life, how much of the sample is left?
a)
1/2
b)
1/3
c)
1/16
d)
1/8
8.
If 10 mg of iodine 131 is given to a patient, how much is left after 24 days? The half-life of iodine-131 is 8 days.
a)
1.25mg
b)
1.25g
c)
10g
d)
10mg
9.

After 22,800 years, approximately what percentage of the original carbon-14 remains?

a)

15%

b)

12.5%

c)

6.25%

d)

3.125%

10.

The % of the parent isotope remaining after 1 Half Life.

a)

50%

b)

25%

c)

12.5%

d)

6.25%

11.

The diagram shows 32 atoms

32 of the Red are the parent isotope

0 of the atoms are daughter isotopes

How many half-lives have occurred?

a)

0

b)

1

c)

2

d)

3

12.

From the nuclear belt of stability, you can see that

a)

As atoms increase in atomic number, more neutrons are needed to achieve a stable isotope

b)

As atoms increase in atomic number, fewer neutrons are needed to achieve a stable isotope

c)

As atoms decrease in atomic number, more neutrons are needed to achieve a stable isotope

d)

There is no relationship between the atomic number and the number of neutrons

13.

A PET-scan patient is injected with radioactive oxygen-

5, whose half-life is 2 minutes. Approximately what

fraction of the original remains undecayed an hour

later?

a)

About 1/2

b)

About 1/30

c)

About ) (12)30\left(\frac{1}{2}\right)^{30}

d)

About (130)12\left(\frac{1}{30}\right)^{\frac{1}{2}}