Question

# The half-life of a radioactive isotope represents the average time it would take half of a...

The half-life of a radioactive isotope represents the average time it would take half of a collection of this type of nucleus to decay. For example, you start with a sample of 1000 Oxygen-15 (15O) nuclei, which has a half-life of 122 seconds. After 122 seconds, half of the 15O nuclei will have decayed into Nitrogen-15 (15N) nuclei. After another 122s, half of the remaining Oxygen nuclei will have also decayed, and so on. Suppose you start with 4.00×103 15O nuclei and zero 15N nuclei. How many 15O nuclei remain after 122 s has passed?

How many 15N nuclei are there after 122 s has passed?

How many 15O nuclei remain after 244 s has passed?

How many 15N nuclei are there after 244 s has passed?

Suppose you start with 7.86×103 Carbon-14(14C) nuclei. 14C has a half-life of 5730 years and decays into Nitrogen-14(14N) via a beta decay. How much time has passed if you are left with 3.93×103 14C nuclei? (The units for years is 'yr'.)

How much time has passed if you are left with 1.96×103 14C nuclei?

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