Tritium,a radioactive isotope of hydrogen,emits which of the following particles?

How many alpha particles are emitted in the nuclear transformation
$_{84}Po^{215} \xrightarrow{} _{82}Pb^{211}$?

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

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

$A$ radioisotope will not emit

During a $\beta$-decay,the mass of the atomic nucleus