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

half life time

mass after 4 half lives

N(0): starting mass

15.81 years passed

1st half life mass

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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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Label the chart with the appropriate data.

a

b

c

d

% mass at starting time N(0)

% decayed after 3 half lives

% original isotope after 4 half lives

half life time

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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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If 10 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. N(t)=N₀⋅½^(t/h)

• 1.25mg

• 0.3125mg

• 2.5mg

• 0.625mg

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The half-life of Zn-71 is 2.4 minutes. If one had 100.0 g at the beginning, how many grams would be left after 7.2 minutes has elapsed? N(t)=N₀⋅½^(t/h)

• 100.0g
• 50.0g
• 12.5g
• 8.5g

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