If a radioactive element lies above the belt, which decay mode does it undergo?

If a radioactive element lies above the belt, which decay mode does it undergo?

• A. Beta decay
• B. Positron emission
• C. Electron capture
• D. Alpha decay

Answer: (A)

Nuclei above the belt of stability have too many neutrons relative to protons, so they move toward stability by undergoing beta minus decay. In beta minus decay, a neutron turns into a proton, and an electron (the beta particle) plus an antineutrino is emitted. This increases the atomic number by one while leaving the mass number unchanged, shifting the nucleus closer to the stability line. Positron emission and electron capture would decrease the proton count and are favored for proton-rich nuclei (below the belt). Alpha decay is a separate mode more common in very heavy nuclei. So, the decay mode for nuclei above the belt is beta decay.

Nuclei above the belt of stability have too many neutrons relative to protons, so they move toward stability by undergoing beta minus decay. In beta minus decay, a neutron turns into a proton, and an electron (the beta particle) plus an antineutrino is emitted. This increases the atomic number by one while leaving the mass number unchanged, shifting the nucleus closer to the stability line. Positron emission and electron capture would decrease the proton count and are favored for proton-rich nuclei (below the belt). Alpha decay is a separate mode more common in very heavy nuclei. So, the decay mode for nuclei above the belt is beta decay.