A free neutron decays to a proton but a free proton does not decay to a neutron. This is because

A free neutron decays into a proton, an electron and

A free neutron decays into a proton, an electron and

A free neutron decays spontaneously into

A free neutron decays spontaneously into

Proton can decay into neutron

A free neutron decays spontaneously into,

Assertion: Free Neutron decays into proton, electron and antineutrino Reason : Neutron is unstable outside the nucleus