Phosphonic acids are a class of organic compounds that contain a phosphorus atom bonded to a carbon atom and hydroxyl groups. They are characterized by the presence of a phosphonic group, which is a phosphorus atom double-bonded to an oxygen atom and single-bonded to a hydroxyl group and two organic groups. These compounds are often used in agriculture as herbicides and in various industrial applications. Due to their unique chemical properties, phosphonic acids can act as chelating agents, helping to bind metal ions in solutions. They are also important in the synthesis of phosphonates, which are used in pharmaceuticals and as additives in detergents.