Which among the following minerals contains a radioactive element?

Which of the following is the most stable atom?

Let $m_p$ be the mass of a proton,$m_n$ that of a neutron,$M_1$ that of a $_{10}^{20}Ne$ nucleus,and $M_2$ that of a $_{20}^{40}Ca$ nucleus. Then:

If radium and chlorine combine to form radium chloride,the compound is:

In a radioactive decay,an emitted electron comes from

$A$ nuclear reaction is accompanied by a loss of mass equivalent to $0.01864 \; amu$. The energy liberated is .......... $MeV$.