${ }_{92}^{235} U$ atom disintegrates to ${ }_{82}^{207} Pb$ with a half-life of $10^9 yr$. In the process, it emits $7 \alpha$ particles and $n \beta^{-}$particles. Here, $n$ is
$7$
$3$
$4$
$14$
In the equation ${ }_{13}^{27} Al +{ }_2^4 He \longrightarrow{ }_{15}^{30} P + X ,$ The correct symbol for $X$ is
What is $\alpha -$ , $\beta -$ and $\gamma -$decay ? Write its general formula.
When a radioactive substance emits an $\alpha$- particle, its position in the periodic table is lowered by
A nucleus of lead $Pb _{82}^{214}$ emits two electrons followed by an $\alpha$-particle. The resulting nucleus will have
A certain stable nucleide, after absorbing a neutron, emits $\beta$-particle and the new nucleide splits spontaneously into two $\alpha$-particles. The nucleide is