If the half-life of a certain radioactive nucleus is $1000 \ s,$ the disintegration constant is

During a nuclear explosion,one of the products is $^{90}Sr$ with a half-life of $28.1 \ years$. If $1 \ \mu g$ of $^{90}Sr$ was absorbed in the bones of a newly born baby instead of calcium,how much of it will remain after $10 \ years$ and $60 \ years$ if it is not lost metabolically?

For $Ra^{226}$,the $t_{1/2}$ is $1620 \ years$. From $0.001 \ g$ of $Ra$,how many $\alpha$-particles are released per $min$?

$A$ certain nuclide has a half-life period of $30 \ min$. If a sample containing $600$ atoms is allowed to decay for $90 \ min$,how many atoms will remain (in $atoms$)?

$C-14$ is used in carbon dating of dead objects because

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 $.0$)?