When an unstable nucleus decays by emitting an alpha particle,the atomic mass number A of the nucleus
A)increases by 4.
B)increases by 2.
C)decreases by 2.
D)decreases by 4.
E)remains unchanged.

Question

Quizplus · Accepted Answer

When an unstable nucleus decays by emitting an alpha particle, it loses 2 protons and 2 neutrons, so the atomic mass number A decreases by 4. Therefore, the correct choice is (D) decreases by 4.

When an Unstable Nucleus Decays by Emitting an Alpha Particle,the