When a radioactive substance emits an $\alpha$-particle,its position in the periodic table is lowered by

$A$ nuclear reaction is given by ${}_{Z}X^{A} \to {}_{Z+1}Y^{A} + {}_{-1}e^{0} + \bar{\nu}$,which represents:

Alpha particles are

The atomic mass number of the element thorium is $232$ and its atomic number is $90$. The end product of this radioactive element is an isotope of lead (atomic mass $208$ and atomic number $82$). The number of alpha and beta particles emitted is:

Which of the following is emitted, when ${ }_{94}^{239} Pu$ decays into ${ }_{92}^{235} U$?

Explain the basic nuclear process by equation in $\beta$-decay.