Atoms & Nuclei

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168 of 239

Question 168 of 239

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

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Answer: (D) neutron has larger rest mass than proton

Mass of the neutron is mn=1.67493×10−27kg{m}_{n}=1.67493\times {10}^{-27}kg,
mass of the proton is mp=1.67262×10−27kg{m}_{p}=1.67262\times {10}^{-27}kg.
Proton's rest mass is less than that of a neutron's rest mass. As particle can not decay to a state of greater mass, hence the proton does not decay to neutron outside nucleus whereas the neutron can decay into a proton though β\beta-decay.

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