Chemistry Regents Practice Test

Which particle is recognized as having the least mass?

1. Proton

2. Neutron

3. Beta particle

4. Alpha particle

The correct answer is: Beta particle

The beta particle is indeed recognized as having the least mass among the options provided. A beta particle is essentially an electron (or a positron) that is emitted during the process of beta decay of a nucleus. Electrons, which make up beta particles, have a very small mass—approximately 1/1836 of the mass of a proton. In contrast, protons and neutrons, which make up the nucleus of an atom, have much greater masses—about 1 atomic mass unit each. The alpha particle, consisting of two protons and two neutrons (essentially a helium nucleus), has a significant mass compared to both protons, neutrons, and beta particles. Therefore, the beta particle, being the lightest, is the correct answer in this context. Understanding the relative masses of these particles is fundamental in nuclear chemistry and particle physics.