β⁻ Decay Increases Proton Number and Emits Antineutrino

Steps:

• Nucleus X has proton number Z and undergoes β⁻ decay, where a neutron converts to a proton.
• This increases the proton number of daughter nucleus Y to Z + 1.
• A β⁻ particle (electron) is emitted to balance charge.
• An antineutrino is emitted as particle P to conserve lepton number, energy, and momentum.

Why B is correct:

• In β⁻ decay, the process n → p + e⁻ + \bar{\nu}_e results in Y having Z + 1 protons and P as the antineutrino.

Why the others are wrong:

• A: Proton number of Y is Z + 1, not Z - 1 (which applies to β⁺ decay).
• C: P is antineutrino, not neutrino; Z - 1 is incorrect for Y.
• D: P is antineutrino, not neutrino.

Final answer: B