The unit for the radioactive decay constant is:

The half-life of $^{60}Co$ is $7 \ years$. If $1 \ g$ of it decays,the amount of the substance remaining after $28 \ years$ is (in $g$)

Radioactive lead $_{82}Pb^{201}$ has a half-life of $8 \ hours$. Starting from $1 \ mg$ of this isotope,how much will remain after $24 \ hours$?

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 $.0$)?

The decay of $_{92}U^{235}$ is a reaction of .......... order.

The $T_{1/2}$ of $C^{14}$ isotope is $5770$ years. The time after which $72\%$ of the isotope is left is .......... years.