$A$ radioactive nucleus undergoes a series of decays according to the scheme
$A \xrightarrow{\alpha} A_1 \xrightarrow{\beta} A_2 \xrightarrow{\alpha} A_3 \xrightarrow{\gamma} A_4$
If the mass number and atomic number of $A$ are $180$ and $72$,respectively,then what are these numbers for $A_4$?

Give a brief explanation about radioactivity.

In the given nuclear reaction,the element $X$ is:
${ }_{11}^{22} Na \rightarrow X + e ^{+} + \nu$

What does the nuclear reaction $_z{X^A} \to {_{z + 1}}{Y^A} + {_{ - 1}}{e^0} + \bar \nu$ represent?

Statement-$1$: $A$ nucleus having energy $E_{1}$ decays by $\beta^{-}$ emission to a daughter nucleus having energy $E_{2}$,but the $\beta^{-}$ rays are emitted with a continuous energy spectrum having an end-point energy $E_{1} - E_{2}$.
Statement-$2$: To conserve energy and momentum in $\beta$ decay,at least three particles must take part in the transformation.

How many energy rays of $\alpha$-particles are emitted from $_{83}^{214}Bi$?