A chemical species refers to any identifiable form of matter with distinct chemical properties. This can include atoms, molecules, ions, or even complexes. For example, a single oxygen atom, a water molecule (H₂O), or a sodium ion (Na⁺) are all considered different chemical species. Each species has unique characteristics that determine how it interacts with other substances. Chemical species can exist in various states, such as solid, liquid, or gas, and can participate in chemical reactions. Understanding these species is crucial in fields like chemistry and biochemistry, as they help scientists predict how substances will behave under different conditions.