Binary acids are certain molecular compounds in which hydrogen is combined with a second nonmetallic element.
Their strengths depend on the solvation of the initial acid, the H-X bond energy, the electron affinity energy of X, and the solvation energy of X. Observed trends in acidity correlate with bond energies, the weaker the H-X bond, the stronger the acid. For example, there is a weak bond between hydrogen and iodine in hydroiodic acid, making it a very strong acid.
The names of binary acids begin with hydro- followed by the name of the other element modified to end with -ic.
Some texts contrast two types of acids. 1. binary acids or hydracids and 2. oxoacids that contain oxygen.