Which of the following describes the hydronium ion (H3O+)?

The hydronium ion (H3O+) is indeed formed when water acts as an acid by donating a proton (H+). In aqueous solutions, when an acid dissolves in water, it donates protons to water molecules, resulting in the formation of hydronium ions. This reaction highlights the role of H3O+ in acid-base chemistry, as it is the species that results from water's interaction with protons.

In this context, considering the properties of acids and bases, hydronium plays a central role in describing the strength of acids in solution. The presence of hydronium ions in water indicates an increase in acidity, reinforcing the concept that hydronium is the principal form of protons in aqueous solutions.

The other options do not accurately describe the hydronium ion's structure or formation pathway. The hydronium ion is not formed by the loss of a hydrogen atom nor by the addition of a hydroxide ion, as these processes do not lead to the creation of H3O+. Additionally, H3O+ is not neutral; it carries a positive charge, which enables its participation in acid-base reactions. Thus, option C correctly encapsulates the essential characteristics and role of the hydronium ion