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

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

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

If the initial concentration of N2O5 is 0 If the initial concentration of N2O5 is 0.80 M, what is the concentration after 5 half- lives? 0.025 M

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

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