What is formed when a hydrogen ion (H+) is added to a water molecule (H2O)?

When a hydrogen ion (H+) is added to a water molecule (H2O), it forms a hydronium ion (H3O+). This occurs because the hydrogen ion, which is simply a proton, combines with the water molecule, effectively resulting in the addition of an extra hydrogen atom to the water's structure.

The formation of a hydronium ion is a crucial process in acid-base chemistry. When acids dissolve in water, they donate protons to water molecules, yielding hydronium ions, which are responsible for the acidic properties of the solution. In aqueous solutions, the presence of hydronium ions means that the solution is acidic, which is central to understanding pH and the behavior of acids in water.

Hydroxide ions and salts arise from different chemical processes, while a solution is a broader term referring to a homogeneous mixture, which, while relevant to the context, does not specify the species formed from the interaction of H+ with water. Hence, hydronium ions are the specific products of this interaction, solidifying the importance of recognizing their role in chemistry.