Radioactive Decay Review3

How old is a fossil that has radioactively decayed through 4 half-lives of carbon-14?

• 5,700 years

• 17,100 years

• 22,800 years

• 28,500 years

Tags

NGSS.HS-PS1-8

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

Tags

NGSS.HS-PS1-8

Radioactive dating of fossils and rocks is possible because radioactive isotopes:

• are found in all fossils and rocks

• are easily collected and measured

• disintegrate into organic substances

• disintegrate at a predictable rate

Tags

NGSS.HS-PS1-8

What percentage of rubidium-87 atoms will be left after four half lives?

• 25.0%

• 12.5%

• 6.25%

• 3.125%

Tags

NGSS.HS-PS1-8

Which diagram represents the correct proportion of 87Rb to its decay product, 87Sr, after two half-lives?

• Diagram A

• Diagram B

• Diagram C

• Diagram D

Tags

NGSS.HS-PS1-8

A fossil formed 11,400 years ago. Which percentage of the original amount of carbon-14 remains in the fossil?

• 100%

• 50%

• 25%

• 12.5%

Tags

NGSS.HS-ESS2-6

How many half-lives have passed if a sample contains 25% of its original carbon-14?

• 1 half-life

• 2 half-lives

• 3 half-lives

• 4 half-lives

A sample of wood that originally contained 100 grams of carbon-14 now contains only 25 grams of carbon-14. Approximately how many years ago was this sample part of a living tree?

• 2,850 years

• 5,700 years

• 11,400 years

• 17,100 years

Tags

NGSS.HS-PS1-8

What does Potassium-40 disintegrate into as it decays?

• Nitrogen-14

• Argon-40

• Lead-206

• Rubidium 8-7

Tags

NGSS.HS-PS1-8