Half Life

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

• 50%

• 25%

• 12.5%

• 6.25%

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

• 50%

• 25%

• 12.5%

• 6.25%

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

If one-fourth of the carbon-14 is remaining then how many half-lives have passed?

• 1
• 2
• 3
• 4

If the half life of a radioactive element is 100yrs, how long would it take for the radioactivity to reduce by one half?

• 200yrs

• 100yrs

• 50yrs

• 300yrs

A certain radioactive sample has a half life of 2 years. After 6 years, how much of the sample is left?

• 1/2

• 1/3

• 1/16

• 1/8

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 4.8 minutes has elapsed?

• 100.0g

• 25.0g

• 12.5g

• 8.5g

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?

• 100.0g

• 25.0g

• 12.5g

• 8.5g

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.

• 1.25mg
• 1.25g
• 10g
• 10mg

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?

• 3.0g
• 0.25mg
• 0.3g
• 0.25g