If a radioactive atom emits a beta particle, Its mass number
Answer Details
When a radioactive atom emits a beta particle, a neutron in the nucleus is converted into a proton and an electron. The electron is emitted as a beta particle, while the proton remains in the nucleus. Therefore, the atomic number increases by one, as the nucleus now has one more proton. The mass number, which is the sum of the protons and neutrons in the nucleus, remains the same, since the neutron is converted into a proton, and the mass of a proton is approximately equal to that of a neutron. So, the correct answer is: "remains the same".