The reaction 210Pb 82 → 210Bi 83 + β- + ν is an example of which process?

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

Answer: (B)

This is beta decay, specifically beta minus decay. In beta minus decay a neutron inside the nucleus converts into a proton, releasing an electron (the beta particle) and an antineutrino. The mass number stays the same while the atomic number increases by one. Here, lead-210 (Z = 82) becomes bismuth-210 (Z = 83) with emission of a beta particle and a neutrino, matching the beta minus process. Other processes would change the mass number differently or involve different particles: alpha decay would reduce the mass and charge more, electron capture would lower the atomic number without emitting a beta particle, and positron emission would decrease the atomic number.