[1] Under Lavoisier's original theory, all acids contained oxygen, which was named from Ancient Greek: ὀξύς + -γενής, romanized: oxys + -genes, lit.
All oxyacids have the acidic hydrogen bound to an oxygen atom, so bond strength (length) is not a factor, as it is with binary nonmetal hydrides.
In that case, the bond between the oxygen and hydrogen atom is weak, and the compound ionizes easily in the way of the former of the two chemical equations above.
In this case, the compound XOH is an acid, because it releases a proton, that is, a hydrogen ion.
If, however, the electronegativity of X is low, then the compound is dissociated to ions according to the latter chemical equation, and XOH is an alkaline hydroxide.
In most cases, the element X is a nonmetal, but some metals, for example chromium and manganese, can form oxyacids when occurring at their highest oxidation states.
Because of this, he gave to this element its name, oxygenium, derived from Greek and meaning acid-maker, which is still, in a more or less modified form, used in most languages.
In light of the current chemical nomenclature, this practice is an exception, because systematic names of compounds are formed according to the elements they contain and their molecular structure, not according to other properties (for example, acidity) they have.
[7] IUPAC, however, recommends against calling future compounds not yet discovered with a name ending with the word acid.
If there are more than two oxyacids having the same element as the central atom, then, in some cases, acids are distinguished by adding the prefix per- or hypo- to their names.
Prefixes hypo- and per- occur in the name of anions and salts; for example the ion ClO−4 is called perchlorate.
[8] In a few cases, the prefixes ortho- and para- occur in names of some oxyacids and their derivative anions.
[10] In the following table, the formula and the name of the anion refer to what remains of the acid when it loses all its hydrogen atoms as protons.