Which of the following pairs of subatomic particles are approximately equal in mass?

• A. Neutron and electron
• B. Proton and neutron
• C. Electron and proton
• D. Proton and electron

Answer: (B)

Verified step by step guidance

1. Recall the approximate masses of the three main subatomic particles: proton, neutron, and electron. The proton and neutron each have masses close to 1 atomic mass unit (amu), while the electron's mass is much smaller, about 1/1836 of a proton's mass.
2. Compare the mass of the proton and neutron: both are roughly 1 amu, so their masses are approximately equal.
3. Compare the mass of the electron with the proton: the electron is significantly lighter, so their masses are not approximately equal.
4. Compare the mass of the electron with the neutron: since the neutron's mass is close to 1 amu and the electron's mass is much smaller, they are not approximately equal.
5. Conclude that the pair with approximately equal masses is the proton and neutron.