During the radioactive decay of a substance,which of the following is $NOT$ emitted?

The number of $\alpha$ and $\beta^-$ particles emitted during the radioactive decay chain starting from ${}_{88}^{226}Ra$ and ending at ${}_{82}^{206}Pb$ is:

Which one of the following cannot emit $\gamma$-radiation and why? $(i)$ Excited nucleus,(ii) Excited electron.

$A$ radioactive nucleus undergoes $\alpha$-emission to form a stable element. What will be the recoil velocity of the daughter nucleus if $V$ is the velocity of $\alpha$-emission and $A$ is the atomic mass of the radioactive nucleus?

What is gamma decay? Explain with a proper example.

In the following equation representing $\beta^{-}$ decay,the number of neutrons in the nucleus $X$ is ${ }_{83}^{210} Bi \longrightarrow X + { }_{-1}^{0} e + \bar{\nu}$