Answer: The isotopic symbol of unknown particle is [tex]_{2}^{4}\textrm{He}[/tex]
Explanation:
In a nuclear reaction, the total mass and total atomic number remains the same.
For the given fission reaction:
[tex]^{228}_{90}\textrm{Th}\rightarrow ^A_Z\textrm{X}+^{224}_{88}\textrm{Ra}[/tex]
To calculate A:
Total mass on reactant side = total mass on product side
228 = A + 224
A = 4
To calculate Z:
Total atomic number on reactant side = total atomic number on product side
90 = Z + 88
Z = 2
Hence, the isotopic symbol of unknown particle is [tex]_{2}^{4}\textrm{He}[/tex]
