Question

What is the change in atomic mass number when an atom emits an alpha particle?

a.
decreases by 2
c.
increases by 2
b.
decreases by 4
d.
increases by 4

Answer 1

Decreases by 4

Step-by-step explanation:

• An alpha particle is made of two protons and two neutrons. An alpha decay involves the ejection of an alpha particle from the nucleus.
• Therefore since an alpha particles is equivalent to a helium nucleus, it involves the loss of 2 protons and 2 neutrons.
• Hence, we can conclude that when a nucleus emits an alpha particle, the mass number or the atomic mass decreases by 4 and the atomic number decreases by 2.