Question

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

• A. neutron is an uncharged particle
• B. neutron has larger rest mass than proton
• C. neutron is a composite particle made of a proton and an electron
• D. proton is a charged particle

Answer 1

Answer: (B)

neutron has larger rest mass than proton

Answer 2

Neutrons and protons are nucleons, but neutronsare not composed of a proton and an electron. Neutrons have no net electric charge, so the electric force has a weaker effect on them.

• Free neutrons are unstable and undergo beta decay, with a mean lifetime of around 15 minutes.
• This decay is possible because the neutron's mass is slightly greater than that of a proton.
• In contrast, free protonsare stable and do not decay into neutrons.
• Neutron decay involves the conversion of a neutron into a proton, an electron, and an electron antineutrino.

The correct answer is (b) a neutron has a larger rest mass than a proton.

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