In 1919, Alfred Stock developed a system of naming inorganic compounds by adding a parentheses after the cation. The oxidation number (number of electrons lost) is placed in the parentheses. For example, Iron(II) is Fe2+ and Iron(III) is Fe3+.
In contrast, nonmetals bound together are named with Greek prefixes. For example, NO2 is nitrogen dioxide.

In 1919, Alfred Stock developed a system of naming inorganic compounds by adding a parentheses after the cation. The oxidation number (number of electrons lost) is placed in the parentheses. For example, Iron(II) is Fe2+ and Iron(III) is Fe3+.

In contrast, nonmetals bound together are named with Greek prefixes. For example, NO2 is nitrogen dioxide.