Radiometric Dating

Identify the Isotope being used

Identify the length of one half-life for that PARENT isotope

Identify the percentage or fraction of the PARENT isotope remaining in the substance

Determine how many half-lives a substance has experienced based on the remaining PARENT isotope

Figure out the amount left or the time passed based on the amount of half lives

The half-life of Carbon-14 is 5730 years before it turns into Nitrogen-14 gas. If 1/8th of a sample is left as Carbon-14, how old is the sample?

1.) Isotope = Carbon-14

2.) Half-life of Carbon-14 = 5730 years

3.)  Remaining parent = ⅛

4.) ⅛ of sample =  3 half-lives

5.) 3 x 5730 years = 17190 years

ANSWER = The sample is 17190 years old

If an object is 500 grams and only 125 grams are the unstable isotope radium-226, which has a half-life of 1600 years, how old is the object?

1.) Isotope = Radium-226

2.) Half-life of radium-226 = 1600 years

3.) Remaining parent = 125/500 = .25 = 25% = ¼

4.)  ¼ of sample = 2 half lives

5.) 2 x 1600 years = 3200 years

ANSWER = The object is 3200 years old.