Radioactive Dating of Fossils

Base your answer on the graph below. The graph shows the number of radioactive Isotope X atoms present as a sample of the isotope undergoes radioactive decay.

Based on the graph, the half-life of this radioactive isotope is

• 6 hours

• 9 hours

• 3 hours

• 12 hours

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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

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NGSS.HS-PS1-8

The graph shows the radioactive decay of rubidium-87.

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

How old is a bone that has 12.5% of the original amount of radioactive carbon-14 remaining?

• 5,700 years

• 17,100 years

• 11,400 years

• 22,800 years

Radioactive decay of ⁴⁰K atoms in an igneous rock has resulted in a ratio of 25 percent ⁴⁰K atoms to 75 percent ⁴⁰Ar and ⁴⁰Ca atoms. How many years old is this rock?

• 2.6 × 10⁹ y

• 1.3 × 10⁹ y

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-PS1-8

The graph shows the decay of a radioactive material over time.

How long does it take for this radioactive material to decay through 2 half-lives?

• 1 × 10³ years

• 10 × 10³ years

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NGSS.HS-PS1-8

How old is a fossil that has radioactively decayed through 3 half-lives of carbon-14?

• 5,700 years

• 17,100 years

• 22,800 years

• 28,500 years

Tags

NGSS.HS-PS1-8

Base your answer to this question on the graph , which shows the generalized rate of decay of radioactive isotopes over 5 half-lives.

Which radioactive isotope takes the greatest amount of time to undergo the change shown on the graph?

• potassium-40

• rubidium-87

Tags

NGSS.HS-PS1-8

The graph shows the radioactive decay of a 50-gram sample of a radioactive isotope.

According to the graph, what is the half-life of this isotope?

• 100 years 

• 200 years

• 350 years

• 600 years

Tags

NGSS.HS-PS1-8