Half-Life of Radioisotopes

Go to the all year 9 stile classroom and complete the task called:

"Phase 2: Periodic Trends"

Half-Life of Radioisotopes

What is decay again?

You may remember from our previous lessons that isotopes of an element may have too much energy inside the nucleus and force out this extra energy to become stable.

​An isotope is a different form of the same element but with a different number of neutrons!

​There were three different ways an atom can do this...can you remember what they're called?

What is half-life?

The decay of radioisotopes is spontaneous and we can't predict when an atom will decay. We can, however, measure the amount of time a sample takes to decay.

Half-Life: The time it takes for half of the atoms in a radioactive substance to decay to a more stable atom. Different radioisotopes have different half-lives, ranging from fractions of a second to millions of years.

Understanding Decay

During each half-life, the amount of the original radioactive material decreases by 50%.

The half-life is constant and does not depend on the amount of substance.

For example, the half-life of carbon-14 is 5730 years.

This means that if you have a sample of carbon-14 with 10g, 5g of these atoms are expected to decay over the course of 5730 years.

Some of the atoms may decay right away, while others will not decay for many thousands more years.

Carbon-14

Multiple Choice

The percentof the parent isotope remaining after 1 half-life is:

• 50%

• 25%

• 12.5%

• 6.25%

Multiple Choice

The percentage of the parent isotope remaining after 3 half-lives is:

• 50%

• 25%

• 12.5%

• 6.25%

Multiple Choice

What is the half-life of this isotope?

• 5 seconds

• 10 seconds

• 15 seconds

• 20 seconds

Multiple Choice

The half-life of Californium-252 is 5 years.

• True

• False