(i) When α - particle is emitted from a radioactive nucleus then atomic number decreases by 2 and atomic mass decreases by 4 . (ii) When β - particle emitted from a radioactive nucleus then atomic number is increased by 1 and atomic mass unaffected. Here, atomic number (Z)=92 After emitting 8α - particles and 6β - particles, Z=92−2×8+6=82 and atomic mass, A=238 ∴A=238−4×8=206