Half-Life

Front

What is half-life?

Back

The time required for half of the radioactive atoms in a sample to decay.

Front

Why do some elements have half-lives?

Back

They radioactively decay.

Front

What is the half-life of iodine-131?

Back

8 days.

Front

After one half-life, what fraction of the original sample remains?

Back

1/2.

Front

After two half-lives, what fraction of the original sample remains?

Back

1/4.

Front

After three half-lives, how much of the sample is left?

Back

1/8.

Front

What is the only difference between two different isotopes of the same element?

Back

Number of neutrons.

Front

What percentage of the parent isotope remains after one half-life?

Back

50%.

Front

What percentage of the parent isotope remains after two half-lives?

Back

25%.

Front

What percentage of the parent isotope remains after three half-lives?

Back

12.5%.