KEAM 2018 Physics and Chemistry Paper

(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