- Isotope
- Ion
- Molecule
- Radical
An ion is an atom or molecule that has gained or lost one or more electrons, acquiring a net electric charge. When an atom loses electrons, it becomes positively charged (cation) because protons now outnumber electrons. When it gains electrons, it becomes negatively charged (anion) due to excess electrons. This process, called ionization, fundamentally changes the atom’s chemical properties and reactivity. Cations are typically formed by metals (e.g., Na⁺, Ca²⁺, Al³⁺), while nonmetals tend to form anions (e.g., Cl⁻, O²⁻). Ions are crucial in countless contexts: electrolyte balance in living organisms, nerve impulse transmission, muscle contraction, and battery function. Ionic compounds form when cations and anions electrostatically attract, creating crystal lattices like sodium chloride (NaCl). The charge magnitude indicates how many electrons were gained or lost—for example, Mg²⁺ lost two electrons. Unlike isotopes (varying neutrons) or radicals (unpaired electrons), ions specifically involve charge imbalance. Understanding ions is essential in chemistry, biology, medicine, and materials science, from pH regulation to electrochemical processes and semiconductor doping.
