Neptunium-239 has a half-life of 2.35 days.How many days must elapse for a sample of ²³⁹Np to decay to 3.00% of its original quantity?

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Quizplus · Accepted Answer

To find the number of days for a sample to decay to 3.00% of its original quantity, we use the half-life formula. The formula to calculate the time for a substance to decay to a certain percentage of its original amount is $t = \frac{\ln(\frac{final\ amount}{initial\ amount})}{\ln(0.5)} \times half\ life$. For a decay to 3.00% (or 0.03 of its original quantity), and given the half-life of Neptunium-239 is 2.35 days, we substitute into the formula: $t = \frac{\ln(0.03)}{\ln(0.5)} \times 2.35$. This calculation results in approximately 11.9 days, which means it takes about 11.9 days for the sample to decay to 3% of its original quantity.

Neptunium-239 Has a Half-Life of 2