1. Time it takes for ½ of a radioisotope to decay
HALF-LIFE
Time it takes for ½ of a radioisotope to decay

2. If an isotope has a half-life of 50 million years, and ⅛ of the sample remaining consists of that isotope, the age of the rock from which it was taken is . . .
150 million years

3. Consider the half-life of potassium 40, which is 1
Consider the half-life of potassium 40, which is 1.3 billion years, what fraction of the original potassium 40 can be expected within a given mineral crystal after 3.9 billion years?
1/8

4. If the initial concentration of N2O5 is 0
If the initial concentration of N2O5 is M, what is the concentration after 5 half- lives?
0.025 M

5. 14 days, 28 days, 42 days, 70 days or 56 days?
The half-life of P-32 is 14 days. How long after a sample is delivered can a laboratory wait to use a sample in an experiment if they need at least 10% of the original radioactivity?
14 days, 28 days, 42 days, 70 days or 56 days?
42 days

6. A piece of fossilized wood has a carbon-14 radioactivity that is ¼ that of new wood. The half-life of carbon-14 is 5730 years. How old is the wood?
11,460 years