Given the question: Answer the following question given this paragraph: Chadwick's work resulted in a new understanding of the nucleus of the atom; it is comprised of both protons and neutrons. Because the masses of subatomic particles are so small, a new unit, called an atomic mass unit (amu), was defined. Protons and neutrons each have a mass of approximately one amu. The Table below describes the characteristics of the three subatomic particles we have discussed. Q: Because the masses of subatomic particles are so small, a new unit, called what, was defined? Choices: - atomic volume unit - particle mass unit - nuclear mass unit - atomic mass unit A:
The answer is:
atomic mass unit