What is the half-life of iodine-131?

• 32 days
• 8 days
• 16 days
• 24 days

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NGSS.HS-PS1-8

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

• 50%

• 25%

• 12.5%

• 6.25%

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NGSS.HS-PS1-8

The % of the parent isotope remaining after 2 Half Lives.

• 50%

• 25%

• 12.5%

• 6.25%

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NGSS.HS-PS1-8

What is the Half life of this isotope?

• 5 seconds

• 10 seconds

• 15 seconds

• 20 seconds

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NGSS.HS-PS1-8

What is Half-life?

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

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NGSS.HS-PS1-8

Why do some elements have half-lives?

• they radioactively decay

• half of their atom gets stolen

• They are Twizzlers that break in half

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NGSS.HS-PS1-8

Half life (in radioactivity) is the amount of time it takes for half of a radioactive sample to

• split.

• combine.

• decay.

• become parent material.

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NGSS.HS-PS1-8

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?

What do we need to know to answer this question? (Check all that applies)

• the half-life for the given sample

• the number of half-lives passed based on the total time

• to multiply by 2

• if alpha decay occurs

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NGSS.HS-PS1-8

If 20 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.

• 32

• 1.25

• 10

• 2.5

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NGSS.HS-PS1-8

Barium-122 has a half-life of 2 minutes. A fresh sample weighing 80 g was obtained. If it takes 10 minutes to set up an experiment using barium-122, how much barium-122 will be left when the experiment begins?

• 0.25g

• 2.5g

• 25g

• 80g

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NGSS.HS-PS1-7