Radioactivity was discovered by

Actinium $231$,${}^{231}Ac_{89}$,emits in succession two $\beta^-$ particles,four $\alpha$ particles,one $\beta^-$ particle,and one $\alpha$ particle,plus several $\gamma$ rays. What is the resultant isotope?

$A$ nucleus with mass number $220$ is initially at rest. It emits an $\alpha$-particle. If the $Q$-value of the reaction is $5.5 \, MeV$,then the kinetic energy of the $\alpha$-particle will be .......... $MeV$.

When $_{90}Th^{238}$ transforms into $_{83}Bi^{222}$,the number of $\alpha$ and $\beta$ particles emitted are:

In the given radioactive decay,the number of $\alpha$ and $\beta$ particles emitted are respectively: $_{90}X^{200} \rightarrow _{80}Y^{168}$

When ${}_{92}U^{238}$ changes into ${}_{82}Pb^{206}$,the number of $\alpha$ and $\beta^-$ particles emitted are: