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When an unstable radioactive atom decays, it usually turns into:

• a more stable atom
• a less stable atom
• the exact same atom but with less pure energy
• empty space

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

According to the graph, what fraction of the original parent isotope still exists after 3 half lives?

• 0,5000 g
• 0,2500 g
• 0,1250 g
• 0.0625 g

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

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

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

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

Potassium-40 is useful for radioactive dating of Earth's rocks because the half-life of potassium-40 

• decreased as the amounts of ⁴⁰Ar and ⁴⁰Ca in the rock increased
  
• remained constant during the radioactive decay process
  
• increased as pressure from the overlying sedimentary rock increased
  
• was shortened by the high temperature of the magma that formed the rock 

The characteristic of the radioactive isotope uranium-238 that makes this isotope useful for accurately dating the age of a rock is the isotope’s 

• organic origin
• constant half life
• common 
  occurrence in sediment
• resistance to weathering