Answer: The original element is [tex]_{84}^{212}\textrm{Po}[/tex]
Explanation:
Alpha decay is defined as the process in which alpha particle is emitted. In this process, a heavier nuclei decays into a lighter nuclei. The alpha particle released carries a charge of +2 units.
The released alpha particle is also known as helium nucleus.
[tex]_Z^A\textrm{X}\rightarrow _{Z-2}^{A-4}\textrm{Y}+_2^4\alpha[/tex]
For the given alpha decay process of an isotope:
[tex]^{Z}_{A}\textrm{X}\rightarrow ^{208}_{82}\textrm{Pb}+_2^4\alpha[/tex]
To calculate A:
Total mass on reactant side = total mass on product side
A = 208 + 4
A = 212
To calculate Z:
Total atomic number on reactant side = total atomic number on product side
Z = 82 + 2
Z = 84
The isotopic symbol of unknown element is [tex]_{84}^{212}\textrm{Po}[/tex]
Hence, the original element is [tex]_{84}^{212}\textrm{Po}[/tex]
