Explain the Stock notation theory with examples.

The oxidation number or state of a metal in a compound is sometimes presented according to the notation given by the German chemist,Alfred Stock,known as Stock notation.
In this system,the oxidation number is expressed by placing a Roman numeral in parentheses immediately after the symbol of the metal in the molecular formula.
This theory is particularly useful for naming metal oxides and other coordination compounds.
Examples:
$Cu_{2}O \rightarrow \text{Copper}(I) \text{Oxide}$
$CuO \rightarrow \text{Copper}(II) \text{Oxide}$
$FeO \rightarrow \text{Iron}(II) \text{Oxide}$
$Fe_{2}O_{3} \rightarrow \text{Iron}(III) \text{Oxide}$
$Na_{2}CrO_{4} \rightarrow \text{Sodium chromate}(VI)$
$K_{2}Cr_{2}O_{7} \rightarrow \text{Potassium dichromate}(VI)$
$V_{2}O_{5} \rightarrow \text{Vanadium}(V) \text{Oxide}$
$Cr_{2}O_{3} \rightarrow \text{Chromium}(III) \text{Oxide}$
$FeSO_{4} \rightarrow \text{Iron}(II) \text{Sulphate}$
$KMnO_{4} \rightarrow \text{Potassium Permanganate}(VII)$
$Mn_{2}O_{7} \rightarrow \text{Manganese}(VII) \text{Oxide}$