Which among the following minerals contains a radioactive element?

The phenomenon of radioactivity arises from the

If the mass defect of ${ }_{5}^{11}B$ is $0.081 \ u$, its average binding energy (in $MeV$) is

$A$ nuclear reaction must be balanced in terms of

In the Thorium series,$_{90}Th^{232}$ loses a total of $6$ $\alpha$-particles and $4$ $\beta$-particles in ten stages. The final isotope produced in the series is

Stable nuclides are those whose $n/p$ ratio is