Hydronium is a positively charged ion formed when a water molecule (H2O) gains an extra hydrogen ion (H+). This ion is represented as H3O+ and plays a crucial role in acid-base chemistry. When acids dissolve in water, they release hydrogen ions, which then associate with water molecules to create hydronium ions. In aqueous solutions, the concentration of hydronium ions determines the acidity of the solution. A higher concentration of H3O+ indicates a more acidic solution, while a lower concentration suggests a more basic or neutral solution. Understanding hydronium is essential for studying chemical reactions in water.