SCH 3U/4C - Nomenclature - Stock Naming System

Some elements have more than one valence they may use when bonding.  The Stock system uses Roman numerals to indicate which valence the element is using in a particular compound.  


Rules for Writing a Name from a Formula

1.     Write down the name of the first element.  This is the element that may have more than one valence.

2.    Include a Roman numeral to represent the valence of the first element (reverse the ‘criss-cross’ to determine the valence).

3.    Remove the ending on the name of the second element and add the “-ide” ending.

ex.(a)  FeCl₂     Fe²   Cl¹       iron (II) chloride

     (b)  FeCl₃     Fe³   Cl¹       iron (III) chloride

    (c)  SnO      Sn¹   O¹        tin (II) oxide          *this is a special case – reversing the criss-cross tells us that the valence of oxide is 1, which is not possible – the valence of oxide must be 2.  This formula must have been reduced to a simplest ratio.  Therefore, reversing the criss-cross should give us:  Sn²   O², giving us the name tin (II) oxide

         

Rules for Writing a Formula from a Name

1.     Write down symbols for the two elements, in the order they appear in the name.

2.    Place the valence of the first element above the first symbol (Roman numeral).

3.    Place the valence of the second element above the second symbol.

4.    Use the ‘criss-cross’ rule and write the numbers as subscripts.

5.    Reduce the subscript numbers to the simplest ratio.

ex.(a)  copper (II) oxide            Cu²   O²  ↝  Cu₂O₂  ↝  CuO

     (b)  chromium (III) sulfide     Cr³   S²  ↝   Cr₂S₃

Need a bit more Stock system in your life?  Check out this video.

Homework

Give the correct formula for the following.

1.     copper (I) oxide         

2.    copper (II) oxide

3.    tin (IV) chloride

4.    mercury (II) bromide

5.    iron (III) fluoride

6.    chromium (III) oxide

7.    chromium (II) oxide

8.    iron (II) chloride

9.    sulfur (VI) fluoride

10.  arsenic (III) iodide

11.  lead (II) oxide

12.  cobalt (II) nitride

13.  cobalt (III) sulfide

14.  phosphorus (III) chloride

15.  phosphorus (V) iodide

16.  manganese (III) oxide

17.  nickel (II) oxide

18.  cobalt (III) fluoride

19.  gold (I) bromide

20. lead (II) sulfide

21.  iron (III) phosphide

22. antimony (III) bromide

23. mercury (I) sulfide

24. tin (II) phosphide

25. nitrogen (V) sulfide

26. tin (IV) oxide

27. copper (I) iodide

28. phosphorus (III) chloride

29. sulfur (VI) oxide

30. silicon (IV) chloride

Give the correct name for the following.

1.     SnF₂       

2.    SnF₄

3.    Cu₂S

4.    CuS

5.    Cr₂O₃

6.    SnS

7.    Fe₂O₃

8.    HgCl₂

9.    CoCl₃

10.  Co₃N₂

11.  PbO

12.  As₂S₃

13.  PCl₃

14.  P₂O₅

15.  PbCl₄

16.  Cu₂O

17.  HgI

18.  Fe₂S₃

19.  SbCl₅

20. NCl₃

21.  As₂S₅

22. Au₂O₃

23. NiO

24. SnF₄

25. MnO

26. PCl₅

27. Cu₃N₂

28. Cu₃N

29. PbS 

30. Ni₂O₃

Answer Keys: