Absolute Dating

The half-life of potassium-40 is 1.25 billion years. If you begin with 12 grams of potassium-40, how much is left after two half-lives?

• 12 grams

• 6 grams

• 3 grams

• 1.5 grams

How much of the parent isotope is left after 3 half lives?

• 100%

• 50%

• 25%

• 12.5%

T/F: The Earth is approximately 4.6 Million Years Old

• True

• False

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

• era
• age
• half-life
• eon

The original element that undergoes radioactive decay is known as the...

• daughter element
• half-life
• parent element
• carbon-14

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

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

What percent of carbon-14 would be left after 11,460 years? (2 half lives)

• 100%
• 75%
• 50%
• 25%

Tags

CCSS.HSF.LE.A.4

What percent of carbon-14 would be left after one half-life?

• 100%

• 75%

• 50%

• 25%

Scientists use radioactive decay to measure...

• relative time
• absolute time
• half-lives
• time of day

After four half-lives, what fraction of the original parent isotopes remain?

• 1/4
• 1/16
• 1/8