When an element undergoes beta decay, how do its mass number and atomic number change?

• A. The mass number decreases by 1, and the atomic number increases by 1.
• B. The mass number increases by 1, and the atomic number remains the same.
• C. The mass number remains the same, and the atomic number increases by 1.
• D. Both the mass number and atomic number decrease by 1.

Answer: (C)

Verified step by step guidance

1. Understand what beta decay is: Beta decay occurs when a neutron in the nucleus transforms into a proton and emits a beta particle (an electron) and an antineutrino.
2. Recall that the mass number (A) is the total number of protons and neutrons in the nucleus, while the atomic number (Z) is the number of protons.
3. Since a neutron changes into a proton during beta decay, the total number of nucleons (protons + neutrons) remains the same, so the mass number does not change.
4. Because a neutron becomes a proton, the number of protons increases by 1, so the atomic number increases by 1.
5. Summarize: In beta decay, the mass number remains constant, and the atomic number increases by 1.