In the reaction $_{93}Np^{239} \xrightarrow{} _{94}Pu^{239} + (?)$,the missing particle is

$A$ radioactive nuclide $X$ decays at the rate of $1.00 \times 10^5 \ disintegration \ s^{-1} \ g^{-1}$. Radium decays at the rate of $3.70 \times 10^{10} \ disintegration \ s^{-1} \ g^{-1}$. The activity of $X$ in millicuries $g^{-1}$ $(mCi \ g^{-1})$ is

After the emission of an $\alpha$-particle from the atom $_{92}X^{238}$,the number of neutrons in the resulting atom will be:

$A$ radioisotope will not emit

The radionuclide $_{90}^{234}Th$ undergoes two successive $\beta$-decays followed by one $\alpha$-decay. The atomic number and the mass number respectively of the resulting radionuclide are

$\beta$-particle is emitted in radioactivity by