Nuclear Half-Life

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

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The time it takes for a radioactivity level to drop by a half is is the sample's ___________________.

• quarter life

• whole life

• wonderful life

• half life

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Label the graph with the data from the half life decay of cobalt-60.

a

b

c

d

e

15.81 years passed

mass after 4 half lives

N(0): starting mass

1st half life mass

half life time

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Using this graph, what is the half-life of the strontium?

• 10 years

• 25 years

• 50 years

• 150 years

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What percent of a sample will remain after 2 half-lives have passed?

• 50

• 0

• 12

• 25

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Label the chart with the appropriate data.

a

b

c

d

half life time

% original isotope after 4 half lives

% decayed after 3 half lives

% mass at starting time N(0)

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How much of a 400 g sample remains after 2 half-lives?

• 400 g

• 200 g

• 100 g

• 50 g

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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?

• 100 grams

• 25 grams

• 2 grams

• 50 grams

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Imagine you have 50,000 atoms of uranium-238. If U-238 has a half-life of 4.5 billion years, how many U-238 atoms will be left after 4.5 billion years?

• 25,000

• 50,000

• 12,500

• 0

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After the third half-life, how much of the sample is left?

• 1/2

• 1/3

• 1/16

• 1/8

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