The average life period of a radioactive element is the reciprocal of its

Half-life of a radioactive substance which disintegrates by $75\%$ in $60 \ min$ will be ......... $min$.

$A$ radioactive sample decays to half of its initial concentration in $6.93 \ min$. It further decays half in next $6.93 \ min$. The rate constant for the reaction is ..... $\min^{-1}$

In a radioactive decay,a uranium atom transforms into a lead atom. If a rock sample from the moon contains an equal number of uranium and lead atoms,and the half-life $(t_{1/2})$ for uranium is $4.5 \times 10^9$ years,then the age of the rock will be:

If $1 \ \mu g$ of radium $(^{226}Ra)$ has disintegrated for $500$ years,how many alpha particles will be emitted per second?

The order of a radioactive disintegration reaction is: