When the radioactive isotope ₈₈ R a²²⁶ decays in a series by emission of three alpha ( ) and a beta ( ) particle, the isotope X which remains undecay is

Step-by-step solution

Due to emission of 3 particles, the mass number is reduced by 12 while atomic number is decreased by 6 . Due to emission of particle, the atomic number is increased by one while there is no change in mass number. Now, resulting mass will be decreased by 12 and atomic number is decreased by 5. So, isotope X is ₈₃ X²¹⁴ .