Decrease in atomic number is observed during

$_{11}^{23}Na$ is the more stable isotope of $Na$. Find out the process by which $_{11}^{24}Na$ can undergo radioactive decay.

During a negative $\beta$-decay:

After the emission of one $\alpha$-particle followed by one $\beta$-particle from the atom of $_{92}X^{238}$,the number of neutrons in the atom will be

The number of $\alpha-$ and $\beta-$ particles emitted when a radioactive element $_{90}E^{232}$ changes into $_{86}G^{220}$ will be

Which metal is used in radiation shielding?