Question

A free neutron decays to a proton but a free proton does not decay to a neutron. how can you explain this ?

• A. neutron is a composite particle made of proton and an electron whereas proton is a fundamental particle
• B. neutron is an uncharged particle where as proton is a charged particle
• C. neutron has a larger rest mass than the proton
• D. weak forces can operate in a neutron but not in a proton

Answer 1

Answer: (C)

neutron has a larger rest mass than the proton

Neutrons and protons are both nucleons, hence neutron is not a composite particle made of proton and an electron.
The neutron has no net electric charge, hence the effect of the electric force on neutron is much weaker.
Free neutrons are unstable, having a mean lifetime of just under 15 minutes (881.51.5 s) from a radioactive decay known as beta decay. This decay is possible since the mass of the neutron is slightly greater than the proton.
The free proton is stable hence, does not decay to a neutron.
$n^0\to p^{+}+e^{-}+{\overline{v}}_e$
where, $p^{+}$, $e^{-}$ and ${\overline{v}}_e$ denote the proton, electron and electron antineutrino, respectively.