Which radioactive decay increases the atomic number by 1 while leaving the mass number unchanged by emitting an electron?

Which radioactive decay increases the atomic number by 1 while leaving the mass number unchanged by emitting an electron?

• A. Beta Minus
• B. Alpha Decay
• C. Beta Plus
• D. Gamma Decay

Answer: (A)

In beta minus decay, a neutron inside the nucleus converts into a proton, releasing an electron (the beta particle) and an antineutrino. This conversion increases the number of protons by one, so the atomic number goes up by 1, while the total number of nucleons remains the same, keeping the mass number unchanged. The emitted particle is an electron, not a positron, which distinguishes beta minus from beta plus decay. Other modes either change the mass number (like alpha decay, which also lowers the atomic number) or leave both numbers unchanged (gamma decay) or decrease the atomic number (beta plus). Hence, this process increases Z by 1 with A staying the same.

In beta minus decay, a neutron inside the nucleus converts into a proton, releasing an electron (the beta particle) and an antineutrino. This conversion increases the number of protons by one, so the atomic number goes up by 1, while the total number of nucleons remains the same, keeping the mass number unchanged. The emitted particle is an electron, not a positron, which distinguishes beta minus from beta plus decay. Other modes either change the mass number (like alpha decay, which also lowers the atomic number) or leave both numbers unchanged (gamma decay) or decrease the atomic number (beta plus). Hence, this process increases Z by 1 with A staying the same.