$A$ radioactive element $_{90}X^{238}$ decays into $_{83}Y^{222}$. The number of $\beta$-particles emitted is:

An atomic nucleus $_{90}Th^{232}$ emits several $\alpha$ and $\beta$-radiations and finally reduces to $_{82}Pb^{208}$. It must have emitted:

$A$ nucleus with mass number $184$ initially at rest emits an $\alpha$-particle. If the $Q$ value of the reaction is $5.5\, \text{MeV}$,calculate the kinetic energy of the $\alpha$-particle in $\text{MeV}$.

After the decay of a single $\beta$ particle,the parent and daughter nuclei are

Which of the following statements is true?

In the nuclear reaction,${ }_6^{11} C \rightarrow{ }_5^{11} B + \beta^+ + X$,$X$ stands for