Final answer:
The subatomic particle within an atom's nucleus that has no charge is the neutron. Neutrons are neutral and, along with the positively charged protons, make up the nucleons in the nucleus. Electrons, which are negatively charged, orbit the nucleus and are not nucleons.
Step-by-step explanation:
The subatomic particle that does not have a charge is neutrons (A). Therefore, within the provided options, the correct answer is A) neutrons. Protons carry a positive charge, and electrons carry a negative charge, while neutrons are electrically neutral. It's worth clarifying that the reference to neutrinos in the options is potentially misleading, as neutrinos are a completely different kind of particle and also have no charge, but they are not part of the question. Unlike neutrons, neutrinos are not hadrons and do not reside in the nucleus of atoms.
Atoms that vary in the number of neutrons in their nuclei are called isotopes (B). Isotopes can have the same number of protons (hence the same element) but different numbers of neutrons. This characteristic results in variations in their atomic mass but not in their chemical properties.
To understand the structure of the atom, it is essential to know that protons and neutrons, collectively referred to as nucleons, constitute the nucleus of an atom. In comparison with electrons, both nucleons have much more mass and contribute significantly to the mass of an atom. It is also essential to note that particles and antiparticles have opposite charges. An example is the electron and its antiparticle, the positron, which has a positive charge.