Explain stock notation theory with example.

Explanation

The oxidation number/state of a metal in a compound is sometime presented according to the notation given by German chemist, Altered Stock known as stock notation.
Oxidation number is expressed by putting a Roman numeral.
Oxidation number in parenthesis after the symbol of the metal in the molecular formula. These theory is useful for the metal oxides.
`Cu_(2)Oto` Copper (I) Oxide
CuO `to` Copper (II) Oxide
FeO `to` Iron (II) Oxide
`Fe_(2)O_(3)to` Iron (III) Oxide
`Na_(2)CrO_(4)to` Sodium cromate (VI)
`K_(2)Cr_(2)O_(7)to` Potassium dichromate (VI)
`V_(2)O_(5)to` Vanadium (V) Oxide
`Cr_(2)O_(3)to` Cromium (III) Oxide
`FeSO_(4)to` Iron (II) Sulphate potassium
`KMnO_(4)to` Potassium Permanganate (VII)
`Mn_(2)O_(7)to` Manganese (VII) Oxide