The half-life of radioactive Technetium-99 is 6.0 hours. Find the number of ⁹⁹Tc nuclei necessary to produce a sample of activity 18 µCi. (1 Ci = 3.7 *10¹⁰ decays/second)

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The activity (A) is related to the number of nuclei (N) by A = λN, where λ is the decay constant. λ can be calculated using the half-life (T₁/₂) with λ = ln(2)/T₁/₂. For Technetium-99, λ = ln(2)/(6*3600 s). Given A = 18 µCi = 18 * 10⁻⁶ * 3.7 * 10¹⁰ decays/s, solve for N to find the number of nuclei.

The Half-Life of Radioactive Technetium-99 Is 6