Radioactive Dating

Amount of Parent Isotope Present Amount of Daughter Isotope Present Decay

Amount of Parent Isotope Present Amount of Daughter Isotope Present Will DECREASE

Decay Amount of Parent Isotope Present Amount of Daughter Isotope Present Will DECREASE

Decay Amount of Parent Isotope Present Amount of Daughter Isotope Present Will DECREASE Will INCREASE

Decay Amount of Parent Isotope Present Amount of Daughter Isotope Present Will DECREASE Will INCREASE

Ratio of: will INCREASE INCREASE

Ratio of: will INCREASE INCREASE

Good to years

Good to 5 billion years

Earth’s atmosphere contains the element carbon, mainly in the form of carbon dioxide (CO 2 ). Most of the carbon in the atmosphere consists of the stable isotope carbon–12, but a very small fraction is a radioactive isotope called carbon–14. The ratio of in the atmosphere has been relatively constant for the last years.

Earth’s atmosphere contains the element carbon, mainly in the form of carbon dioxide (CO 2 ). Most of the carbon in the atmosphere consists of the stable isotope carbon–12, but a very small fraction is a radioactive isotope called carbon–14. The ratio of in the atmosphere has been relatively constant for the last years.

Earth’s atmosphere contains the element carbon, mainly in the form of carbon dioxide (CO 2 ). Most of the carbon in the atmosphere consists of the stable isotope carbon–12, but a very small fraction is a radioactive isotope called carbon–14. The ratio of in the atmosphere has been relatively constant for the last years.

Earth’s atmosphere contains the element carbon, mainly in the form of carbon dioxide (CO 2 ). Most of the carbon in the atmosphere consists of the stable isotope carbon–12, but a very small fraction is a radioactive isotope called carbon–14. The ratio of in the atmosphere has been relatively constant for the last years.

Carbon from the Environment

While they are still alive, the ratio of remains the same as it is in the environment.

When an organism dies, it stops getting fresh carbon from the environment.

Remains as it is

Decreases as it decays

As the object gets older, the ratio of gradually decreases over time.

Carbon–14 nuclei undergo beta decay:

5730 y

50% of its original carbon–14 will still be present

5730 y

A rib-bone from an archeological site was analyzed. By measuring the ratio of in the sample and comparing it to that in the environment, archeologists calculated that 12.0% of its original remained. How old is the bone?

12.0%

y

years old