PS [M3.L2] Activity 1.Half-Life

What is the half-life of iodine-131?

• 32 days
• 8 days
• 16 days
• 24 days

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 the Half life of this isotope?

• 5 seconds

• 10 seconds

• 15 seconds

• 20 seconds

What is the Half Life of this isotope?

• 3 days

• 5 days

• 8 days

• 10 days

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

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

Why do some elements have half-lives?

• they radioactively decay

• half of their atom gets stolen

• They are Twizzlers that break in half

Radioactive carbon-14 is often useful in determining the absolute age of geologic samples because radioactive isotopes

• decay at a regular rate

• become less stable during decay

• remain unchanged over time

• stabilize after four half-lives