Question

A free neutron decays into a proton, an electron and :

• A. a beta particle
• B. an alphaparticle
• C. an antineutrino
• D. a neutrino

Answer 1

Answer: (C)

Pauli suggested that after emission of $\beta -$ particle (electron) a neutron is converted into a proton in a nucleus and in this reaction an electron and an anti-neutrino $(\overrightarrow{v})$ will be formed. This reaction is represented as $\underset{(Neutron)}{{}_0{n}^1}\to \underset{(\mathrm{Pr}oton)}{{}_1{H}^1}+\underset{(Electron)}{{}_{-1}{\beta }^0}+\underset{(Anti-neutrino)}{\overline{v}}$ Antineutrino is a particle whose mass is negligible and on which no charge is present. $\Rightarrow$ After emission of P-particle, the total number of particles (mass-number) in a nucleus remains unchanged but no. of neutrons reducing by 1 makes the no. of protons (i.e., charge-number) to increase by 1.