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

Question

Quizplus · Accepted Answer

An alpha particle consists of 2 protons and 2 neutrons, so when an alpha particle is emitted, the atomic mass number decreases by 4.

When an Unstable Nucleus Decays by Emitting an Alpha Particle AAA

When an Unstable Nucleus Decays by Emitting an Alpha Particle $A$