The nucleus ${ }_{88}^{226} Ra$ is converted into ${ }_{82}^{206} Pb$ by the emission of alpha $(\alpha)$ and beta $(\beta)$ particles. The number of alpha and beta particles emitted are respectively:

Assertion: ${}_{Z}{X^{A}}$ undergoes $2\alpha$-decays,$2\beta$-decays,and $2\gamma$-decays,and the daughter product is ${}_{Z-2}{X^{A-8}}$.
Reason: In $\alpha$-decays,the mass number decreases by $4$ and the atomic number decreases by $2$. In $\beta$-decays,the mass number remains unchanged,but the atomic number increases by $1$.

In the Uranium radioactive series,the initial nucleus is ${ }_{92}^{238} U$ and the final nucleus is ${ }_{82}^{206} Pb$. When the Uranium nucleus decays to lead,the number of $\alpha$-particles emitted is .......... and the number of $\beta$-particles emitted is ..........

$A$ radioactive element forms its own isotope after $3$ consecutive disintegrations. The particles emitted are

In a radioactive decay process,the atomic number and mass number of the nucleus do not change. Which of the following is emitted during this process?

Alpha particles are