Problem

The nuclide

{}_{11}^{24} \text{Na}

is unstable and has a decay constant of

1.28 \times 10^{-5} \text{ s}^{-1}

. a. a Calculate the half-life of

{}_{11}^{24} \text{Na}

. b. b As a fraction of its initial activity, what would the activity of a sample of

{}_{11}^{24} \text{Na}

be after i 15 hours? ii 30 hours?