Earth Science Reference Table Radioactive Decay Data

Radiometric dating is possible because the rates of decay of radioactive isotopes _____.

• change over time
• change from place to place
• are constant
• vary widely

The time it takes for 50% of the nuclei in a radioactive sample to decay to its stable isotope is called _____.

• the daughter product
• geologic time
• the half-life
• the half-time

You find a rock sample with radioactive atoms present.  If 12.5% of the original radioactive atoms were present, how many half-lives has the rock been around for? (Hint, at Half-Life = 0, you start with 100%)

• zero
• 1
• 2
• 3

You find a rock sample with radioactive atoms present.  If 25% of the original radioactive atoms were present, how many half-lives has the rock been around for? (Hint, at Half-Life = 0, you start with 100%)

• zero
• 1
• 2
• 3

If the half-life of a radioactive group of atoms is 100 years, then how old is the rock if there have been two half-lives?

• 25 years
• 200 years
• 400 years
• 800 years

Suppose you found a material in which 12.5% of the original radioactive atoms were still present.  If the half-life of an atom is 60 years, how old is the material?

• 30 years old
• 60 years old
• 120 years old
• 180 years old

Using ESRT (A) [Radioactive Decay Data], what is the half-life in standard notation of Uranium-238?

• 4,500 years
• 450,000 years
• 4,500,000 years
• 4,500,000,000 years

The table shows the radioactive decay of carbon-14. Part of the table has been left blank. 
After 22,800 years, approximately what percentage of the original carbon-14 remains? 

• 15%
• 12.5%
• 6.25%
• 3.125%

The graph shows the generalized rate of decay of radioactive isotopes over 5 half-lives. 
If the original mass of a radioactive isotope was 24 grams, how many grams would remain after 3 half-lives? 

• 12
• 24
• 3
• 6

Which radioactive isotope takes the greatest amount of time to undergo radioactive decay? 

• Carbon-14
• Potassium-40
• Uranium-238
• Rubidium-87