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Why is H2SO4 called sulfuric acid while H2SO3 is called sulfurous acid?

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Two diagrams show the three-dimensional structure of a methane molecule: panel A uses a ball-and-stick model with a central carbon atom connected to four hydrogen atoms in a tetrahedral arrangement, while panel B illustrates the bond angle of 109.5 degrees and bond length of 1.09 angstroms between carbon and hydrogen atoms. — chemical compound Methane, in which four hydrogen atoms are bound to a single carbon atom, is an example of a basic chemical compound. The structures of chemical compounds are influenced by complex factors, such as bond angles and bond length.

The naming of these acids is based on the nomenclature of the polyatomic ions they contain. When an acid contains oxygen, its name is derived from the suffix of the corresponding anion.12

Sulfuric acid (H₂SO₄) contains the sulfate ion (SO₄²⁻). According to chemical naming conventions, when an anion name ends in -ate, the suffix is replaced by -ic to form the acid's name.31
Sulfurous acid (H₂SO₃) contains the sulfite ion (SO₃²⁻). When an anion name ends in -ite, the suffix is replaced by -ous to name the acid.31

This system allows chemists to distinguish between series of oxyacids based on the number of oxygen atoms present in the molecule. Generally, the -ic suffix indicates a higher number of oxygen atoms, while the -ous suffix indicates a lower number.345