$_{90}^{232}Th$,an isotope of thorium,decays in ten stages,emitting six $\alpha$-particles and four $\beta$-particles in total. The end product of the decay is:

$1$ curie represents

$A$ nucleus $_n^mX$ emits one $\alpha$ particle and two $\beta^-$ particles. The resulting nucleus is

In a radioactive decay chain reaction,${ }_{90}^{230} Th$ nucleus decays into ${ }_{84}^{214} Po$ nucleus. The ratio of the number of $\alpha$ to number of $\beta^{-}$ particles emitted in this process is. . . . .

$\beta$-decay means emission of electron from

$A$ nuclear decay is possible if the mass of the parent nucleus exceeds the total mass of the decay particles. If $M(A, Z)$ denotes the mass of a single neutral atom of an element with mass number $A$ and atomic number $Z$,then the minimal condition that the $\beta^{-}$ decay $X_Z^A \rightarrow Y_{Z+1}^A + \beta^{-} + \bar{\nu}_e$ will occur is ($m_e$ denotes the mass of the $\beta^{-}$ particle and the neutrino mass $m_{\nu}$ can be neglected).