Hydrogen carbonate, represented as HCO3 1-, is an ion that consists of one hydrogen atom, one carbon atom, and three oxygen atoms. The -1 charge indicates that it has gained one electron, giving it a negative charge. This ion is formed when carbonic acid (H2CO3) donates a proton (H+) to water (H2O), resulting in the formation of bicarbonate (HCO3-) and a hydronium ion (H3O+). Hydrogen carbonate is an important ion in chemistry and biology, playing a role in the regulation of pH in the blood and acting as a buffer to maintain the acid-base balance.