Binary Compounds of Cations with Variable Charges
Given Formula, Write the Name
The Stock System
A binary compound is one made of two different elements. There can be one of each element such as in CuCl or FeO. There can also be several of each element such as Fe2O3 or SnBr4.
This lesson shows you how to name binary compounds from the formula when a cation of variable charge is involved. The four formulas above are all examples of this type.
The cations involved in this lesson have AT LEAST TWO charges. The anions involved have only one charge.
Your teacher will hold you responsible for the cations you must learn. The ChemTeam holds their students responsible for: Cu, Fe, Hg, Pb, Sn, Mn, Co, Au, and Cr.
The type of naming you will learn about is called the Stock system or Stock's system. It was designed by Alfred Stock (1876-1946), a German chemist and first published in 1919. In his own words, he considered the system to be "simple, clear, immediately intelligible, capable of the most general application."
In 1924, a German commission recommended Stock's system be adopted with some changes. For example, FeCl2,which would have been named iron(2)-chloride according to Stock's original idea, became iron(II) chloride in the revised proposal. In 1934, Stock approved of the Roman numerals, but felt it better to keep the hyphen and drop the parenthesis. This suggestion has not been followed, but the Stock system remains in use world-wide.
Example #1: Write the name for: FeCl2
Step #1 - the first part of the name is the unchanged name of the first element in the formula. In this example, it would be iron.
Step #2 - the result from step one WILL be followed by a Roman numeral. Here is how to determine its value:
Since the result of step #2 is 2, we then use iron(II) for the name. Notice that there is no space between the name and the parenthesis.
Step #3 - the anion is named in the usual manner of stem plus "ide."
The correct name of the example is iron(II) chloride.
Example #2: name this compound: CuCl2
In this example, I've explained it differently. Compare it to the one above. Example #4 is also explained this way.
This compound is named copper(II) chloride.
Example #3: Write the name for: Fe2O3
Step #1 - the first part of the name is the unchanged name of the first element in the formula. In this example, it would be iron.
Step #2 - the result from step one WILL be followed by a Roman numeral. Here is how to determine its value:
In this example, the result of step #2 is 3. That means that iron(III) will be used for the name. Notice that there is no space between the name and the parenthesis.
Step #3 - the anion is named in the usual manner of stem plus "ide."
The correct name of the example is iron(III) oxide.
This compound is named tin(II) oxide.
Answer using the Stock system.
Write the correct name for:
1) CuS
2) PbBr4
3) Pb3N2
4) Fe2O3
5) FeI2
6) Sn3P4
7) Cu2S
8) SnCl2
9) HgO
10) Hg2F2
Special words about mercury
Answers to Set One
11) CuCl2
12) CuBr
13) PbO
14) Fe2S3
15) PbCl2
16) SnO
17) Cu2O
18) PbO2
19) FeO
20) SnO2 Answers to Set Two
21) Hg2O
22) Hg2I2
23) AuCl3
24) MnO
25) CrCl3
26) CoO
27) Mn2O3
28) Co2S3
29) AuF
30) CrBr2 Answers to Set Three