Question
Physics Question on Nucleus
A nucleus with atomic number Z and mass number A undergoes alpha decay. Which of the following is true?
A
increases by 2 and A decreases by 4
B
decreases by 2 and A decreases by 2
C
increases by 1 and A do not change
D
decreases by 2 and A decreases
Answer
decreases by 2 and A decreases
Explanation
Solution
When a nucleus undergoes alpha decay, it emits an alpha particle. An alpha particle is composed of 2 protons and 2 neutrons, so it has a charge of +2 (due to the 2 protons) and a mass number of 4.
Given this information:
1. The atomic number Z will decrease by 2 because 2 protons are lost.
2. The mass number A will decrease by 4 because the total of 2 protons and 2 neutrons are lost.
So, the correct answer is: D. Z decreases by 2 and A decreases by 4