The ion HSO4-, known as the hydrogen sulfate ion, is a negatively charged polyatomic ion. It consists of one sulfur atom, four oxygen atoms, and one hydrogen atom. The overall charge of the ion is -1, making it an important component in various chemical reactions, particularly in acid-base chemistry. HSO4- can act as both an acid and a base, depending on the reaction conditions. When it donates a proton (H+), it forms the sulfate ion SO4^2-. Conversely, it can accept a proton to form sulfuric acid H2SO4. This dual behavior makes HSO4- a versatile species in many chemical processes.