What is an anion?

• A. A neutral atom
• B. A negatively charged ion
• C. A positively charged ion
• D. An ion that has lost electrons

Answer: (B)

An anion is a negatively charged ion. It forms when an atom or molecule gains electrons, giving it more negative charges than positive charges. The extra electrons create a net negative charge, like chloride ion Cl−. In contrast, a neutral atom has no overall charge, and a positively charged ion (a cation) forms when electrons are lost. An ion that has lost electrons is not an anion. So the defining idea is that an anion is a negatively charged ion resulting from gaining electrons.