Isotope Calculations

What is the Half Life of this isotope?

• 3 days

• 5 days

• 8 days

• 10 days

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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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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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The mass of a parent isotope is 100 g. How many grams of the parent isotope will remain after 2 half-lives?

• 25

• 50

• 12.5

• 0

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^{The photo above shows the isotopic notation for which isotope?}

• Carbon 12

• Carbon 13

• Carbon 14

• Carbon 15

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What is the half-life of iodine-131?

• 32 days

• 8 days

• 16 days

• 24 days

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

• 15%

• 12.5%

• 6.25%

• 3.125%

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

• 50%

• 25%

• 12.5%

• 6.25%

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

• 50%

• 25%

• 12.5%

• 6.25%

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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?

• 0

• 1

• 2

• 3

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