During beta minus decay, what happens to the mass number A?

During beta minus decay, what happens to the mass number A?

• A. A increases by 1
• B. A remains unchanged
• C. A decreases by 1
• D. A increases by 2

Answer: (B)

In beta minus decay, a neutron inside the nucleus is transformed into a proton, plus an emitted electron (the beta particle) and an antineutrino. The total number of nucleons (protons plus neutrons), which is the mass number A, doesn’t change because one nucleon is simply converted into another. So A remains the same. The atomic number Z, however, increases by 1 since there is now one more proton in the nucleus, shifting the element up by one on the periodic table. The emitted beta particle carries energy but does not affect the total nucleon count.

In beta minus decay, a neutron inside the nucleus is transformed into a proton, plus an emitted electron (the beta particle) and an antineutrino. The total number of nucleons (protons plus neutrons), which is the mass number A, doesn’t change because one nucleon is simply converted into another. So A remains the same. The atomic number Z, however, increases by 1 since there is now one more proton in the nucleus, shifting the element up by one on the periodic table. The emitted beta particle carries energy but does not affect the total nucleon count.