Which of the following best describes ions?

Ions are best described as charged particles, which means they have an unequal number of protons and electrons. This charge can be positive or negative, depending on whether there are more protons (positive charge) or more electrons (negative charge). This fundamental characteristic allows ions to interact with other particles in unique ways, such as through electrical attraction or repulsion.

In contrast, neutral particles do not possess a charge because they have equal numbers of protons and electrons. Particles with atomic mass refers to the concept of atomic weight or mass of an atom, which is not solely indicative of the property of being an ion. Isotopes are variations of the same element that have different numbers of neutrons in their nuclei, but this does not inherently define them as ions either. Thus, the clarity and specificity of the definition of ions as charged particles stand out as the most accurate choice in this context.