NTA Abhyas JEE Main2020PhysicsAtomic PhysicsPractice
A nucleus with Z = 92 emits the following in a sequence: α , α , β - , β - , α , α , α , α , β - , β - , α , β + , β + , α . What is the atomic number of the resulting nucleus?
Correct answer
78
Step-by-step solution
The nucleus emits 8 α particles i.e., 8 2 He 4 ∴ Decrease in Z = 8 × 2 = 16 Four β - particles are emitted i.e., 4 - 1 β 0 ∴ Increase in Z = 4 × 1 = 4 2 positrons are emitted i.e., 2 1 β 0 ∴ Decrease in Z = 2 × 1 = 2 ∴ Z of resultant nucleus = 92 - 16 + 4 - 2 = 78.