Chemistry Regents Practice Test

What is the mass of a proton approximately equal to?

1. a neutron

2. a hydrogen atom

3. a carbon atom

4. a positron

The correct answer is: a neutron

The mass of a proton is approximately equal to the mass of a neutron. In atomic terms, both protons and neutrons are nucleons, which are found in the nucleus of an atom, and they have similar masses, with the neutron being slightly heavier. The mass of a proton is about 1.67 x 10^-27 kilograms or 1 atomic mass unit (amu), which is very close to the mass of a neutron, making them comparable. When considering the other entities mentioned, a hydrogen atom consists of one proton and typically one electron, making its total mass slightly less than that of a proton alone due to the relatively negligible mass of the electron. A carbon atom, on the other hand, contains six protons and six neutrons, significantly increasing its mass compared to a single proton. A positron, as the antiparticle of an electron, has a mass similar to that of an electron, which is vastly smaller than that of a proton. Therefore, the approximate equality of the proton and neutron mass is the most accurate and relevant comparison.