Hi Zaid,

Stock notation is nothing it is just a nomancluture with roaman number in it 

I will explain you,

Lets take an example of NO₂

calculate oxidation number of N in this compound -

X - 4 = 0

X = +4  

Now we will write this in format of stock notation 

Nitrogen (IV) Oxide                                  (Answer)

Simple :)

Hope you got it

Thanks for asking 

Good day :)