Naming Chemical Compounds Using The Stock System

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The Stock System uses Roman Numerals in the naming of chemical compounds.

Some elements in the transition elements that makeup compounds carry more than one oxidation charge. How to you determine then which charge the cation element will carry and how does this relate to The Stock Number?

Examples

   Fe²⁺ and Fe³⁺                          Cu¹⁺ and Cu²⁺

  Iron (II)   Iron (III)                 Copper (I)      Copper (II)

Given the compound

FeO

The Compound would be called

Iron (II) Oxide

Let’s look at it more closely:

Fe²⁺   O^-2  The metal atom Fe is the cation, where as the O is the anion. There is a little song I made up and if you sing it will help:

“The anion determines the cation the cation determine the stock number.”

Lets’ try another one:

PbS₂ What is the Stock Name for this compound?

We know that Pb is lead and S is sulfur. We also know that compound oxidation numbers must zero out so if S has a oxidation of -2  and there is 2 S atoms then the anion charge is -4. In order for compound to zero out on oxidation numbers then Pb must have a +4 charge for the cation and then that cation number would be The Stock Number! So the compound would be called:

Lead (IV) Sulfide!