What particle has a positive electrical charge of one unit?

The correct choice is based on the fundamental properties of subatomic particles. A proton is a subatomic particle found in the nucleus of an atom, and it carries a positive electrical charge of one unit. This positive charge is crucial for the stability of atoms, as it helps balance the negative charge of electrons, which orbit the nucleus.

Understanding protons is essential in contexts like chemistry and physics because the number of protons in an atom determines the element’s identity and its position on the periodic table. For instance, hydrogen has one proton, while helium has two. Moreover, the proton's positive charge plays a vital role in forming chemical bonds and interactions between atoms.

In contrast, electrons have a negative charge, neutrons are neutral with no charge, and ions can be either positively or negatively charged depending on the gain or loss of electrons. Thus, the distinguishing characteristic of the proton is its specific positive charge, making it the correct answer in this context.