Which is not emitted by a radioactive substance?

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

Which of the following has the maximum penetrating power?

Which metal is used in radiation shielding?

During the emission of a $\beta$-particle,what happens to the nucleus?

In the decay sequence:
$^{238}_{92}U$ $\xrightarrow{- x_1} ^{234}_{90}Th$ $\xrightarrow{- x_2} ^{234}_{91}Pa$ $\xrightarrow{- x_3} ^{234}_{92}Z$ $\xrightarrow{- x_4} ^{230}_{90}Th$
$x_1, x_2, x_3$ and $x_4$ are particles/radiation emitted by the respective isotopes. The correct option$(s)$ is/are-
$(1)$ $Z$ is an isotope of uranium
$(2)$ $x_2$ is $\beta^{-}$
$(3)$ $x_1$ will deflect towards negatively charged plate
$(4)$ $x_3$ is $\gamma$-ray