What defines anions?

Anions are specifically defined as negatively charged ions that are formed when an atom or molecule gains one or more electrons. This process occurs because electrons carry a negative charge, so when an atom adds electrons, it becomes negatively charged as a result. This definition aligns precisely with the characteristics of anions in chemistry.

For example, a chlorine atom can gain an electron to become a chloride ion (Cl⁻), which is an anion. In this situation, the gain of the electron changes the overall charge of the atom from neutral to negative.

The other options present concepts that are not relevant to the definition of anions. Positively charged ions formed by losing electrons describe cations, whereas neutral particles refer to atoms or molecules that do not possess any charge. Finally, atoms with an equal number of protons and electrons are simply neutral atoms, which do not fall under the definition of anions. Understanding the characteristics of anions helps clarify their role in various chemical reactions and their significance in fields like electrochemistry and corrosion engineering.