Half-life

Front

What is Half-life?

Back

The amount of time it takes for half the nuclei in a sample of the isotope to decay.

Front

If the half-life of uranium-232 is 70 years, how many half-lives will it take for 10 g of it to be reduced to 1.25 g?

Back

3 half-lives.

Front

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

Back

1/8.

Front

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.

Back

1.25 mg.

Front

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?

Back

0.25 g.

Front

What happens to the amount of a radioactive substance after each half-life?

Back

It reduces to half of its previous amount.

Front

If a substance has a half-life of 10 years, how much of a 16 g sample will remain after 30 years?

Back

2 g.

Front

Define radioactive decay.

Back

The process by which an unstable atomic nucleus loses energy by emitting radiation.

Front

What is the formula to calculate the remaining quantity after n half-lives?

Back

Remaining quantity = Initial quantity × (1/2)^n.

Front

If the half-life of a substance is 5 years, how much of a 20 g sample will remain after 15 years?

Back

2.5 g.