Which particle is primarily responsible for determining the charge of an ion?

The charge of an ion is primarily determined by the difference in the number of protons and electrons present in an atom. Protons, which are positively charged particles located in the nucleus of an atom, provide the positive charge, while electrons are negatively charged particles that orbit the nucleus.

When an atom gains or loses electrons, it becomes charged and forms an ion. If an atom loses one or more electrons, it results in a net positive charge, which is characteristic of a cation. Conversely, if an atom gains electrons, it obtains a net negative charge, forming an anion.

In this context, while protons play a crucial role in defining the inherent positive charge of the atom, the actual charge of an ion is influenced directly by the number of electrons compared to the protons. Therefore, the electrons are key to determining whether an ion will have a positive or negative charge.

The options of neutron, positron, and proton are not responsible for changing the charge of an existing ion—neutrons are neutral and do not affect charge, and positrons are not typically found in stable atoms, serving more as a concept in particle physics rather than in standard ion formation in chemistry.