What subatomic particle in an atom carries a negative charge?

In an atom, the subatomic particle that carries a negative charge is the electron. Electrons are fundamental components of atoms, existing in energy levels or shells around the nucleus, which is composed of protons and neutrons. The negative charge of electrons is essential for the formation of chemical bonds and the overall electrical neutrality of atoms when they are not ionized.

Protons, on the other hand, carry a positive charge and are found within the nucleus alongside neutrons, which are neutral and carry no charge at all. Ions, mentioned in the choices, refer to atoms or molecules that have gained or lost electrons, resulting in a net electric charge, but they are not a type of subatomic particle.

Therefore, the electron is the correct answer as it uniquely represents the subatomic particle with a negative charge, which plays a crucial role in the behavior of atoms and their interactions in chemical reactions.