The disintegration constant for a radioactive substance is $0.58 \, hr^{-1}$. Its half-life period is $........ \, hr$.

Initial mass of a radioactive element is $40 \ g$. How many grams of it would be left after $24 \ years$,if its half-life period is $8 \ years$?

The half-life of a radioisotope is $4 \ hours$. If the initial mass of the isotope is $200 \ g$,then the mass remaining after $24 \ hours$ will be ....... $g$.

$1.0 \ g$ of radioactive sodium decays to $0.25 \ g$ in $16 \ hours$. Calculate the time required for $48 \ g$ of the same radioactive sodium to decay to $3.0 \ g$. (in $hours$)

The half-life of a radioactive isotope is $3 \ hours$. If the initial mass of the isotope is $256 \ g$,how much mass in $g$ will remain after $18 \ hours$ (in $.0$)?

$A$ radioactive sample $(Z = 22)$ decreases by $90\%$ in $10 \ \text{years}$. What will be the half-life of the sample in $\text{years}$?