A Level Physics Practice Exam

What is a nucleon?

1. Any atom

2. A proton or neutron in the nucleus

3. An electron outside the nucleus

4. A type of particle associated with quarks

The correct answer is: A proton or neutron in the nucleus

A nucleon refers specifically to either a proton or a neutron, both of which are found in the nucleus of an atom. Nucleons are the building blocks of atomic nuclei and play a crucial role in determining the mass and stability of the atom. The term is derived from their fundamental role in the nuclear structure, as they are the particles that make up the nucleus, contrasting with electrons, which are found outside the nucleus and do not contribute to the atomic mass in the same way. By understanding the definition of a nucleon, it's clear that while all atoms consist of nucleons at their cores, this term is not applicable to an entire atom or to particles outside the nucleus. Additionally, although quarks are the fundamental constituents of nucleons, identifying nucleons purely as quark-associated particles doesn't capture their role in atomic structure. Thus, defining a nucleon as either a proton or a neutron provides clarity regarding its significance and position within atomic physics.