What is an ion?

An ion is fundamentally defined as an atom or a group of atoms that possess a net electric charge. This charge occurs when the number of protons, which are positively charged, does not equal the number of electrons, which are negatively charged. If an atom gains electrons, it becomes negatively charged and is referred to as an anion. Conversely, if it loses electrons, it becomes positively charged, known as a cation. This concept of charge imbalance is crucial in various fields, including chemistry and physics, and plays a significant role in the behavior of substances in different environments, such as in solutions, electrical conductivity, and chemical reactions.

The other answers do not accurately describe an ion. A neutral particle formed by two or more atoms is a molecule, while a molecule without any electric charge is also considered neutral, not fitting the definition of an ion. Lastly, describing an ion as a common element found in nature is misleading, as ions are not elements in themselves but rather charged particles derived from them.