Honors Chemistry

Honors Chemistry Name_______________________

Nomenclature Packet—PMP 4—Ionic Nomenclature

Mr. McAfoos / Mr. Nelson Period_______ Date____________

Formula Writing:

To write the formula of an ionic compound, you must know the valence of each element or radical (polyatomic ion) and/or where this valence can be found. Obvious question: What is valence? Not so obvious answer: Valence is defined as the combining capacity of an atom or radical. This combining capacity (or valance) is (for our purposes) equal to the charge on the atom or radical. Valences can be positive or negative since atoms can gain or lose electrons.

Valences for elements can be found though the periodic table in the following way: All elements tend to become ions that create noble gas electron configurations. So all alkali metals (first column) tend to lose an electron and become +1 ions. Conversely the halogens tend to gain an electron to become -1 ions. For those elements that are more than a few electrons away for a stable configuration several valences are possible. These elements (primarily the transition metals) have valences that vary from one compound to the next. For any element, the table lists the possible charges in small black numbers above the symbol of the element. The valence of a radical is the charge of the radical.

Now that you know what valences are and where and how they can be found, let's use them to learn how to write formulas.

The method for writing formulas follows the mental program given below.

Example #1

Given name of compound

sodium chloride

translate to symbols

Na Cl

assign valence to each symbol

Na⁺¹ Cl^-1

combine so valences add algebraically to zero

(+1) + (-1) = 0

so... NaCl

Example #2

Example #3

Barium chloride

Aluminum sulfide

Ba Cl

Al S

Ba⁺² Cl^-1

Al⁺³ S^-2

(2) + (-1) ¹ 0

(3) + (-2) ¹ 0

(2) + 2(-1) = 0

2(3) + 3(-2) = 0

BaCl₂

Al₂S₃

Now lets take a closer look at what we've done.

1. Notice that each compound is composed of one element with a (+) valance and one element with a (-) valence. The (+) element is always written first; the (-) element last.

2. Since compounds are neutral, the total positive valence must be equal to the total negative valence. Therefore, in a compound such as aluminum sulfide, 1 atom of Al (+3) is NOT balanced by 1 atom of S (-2). Therefore, one needs 2 atoms of Al given a total valance of +6 and 3 atoms of S giving a total valance of -6.

Those metals that have more than one possible valence have this valence indicated by a Roman numeral following the name of the metal in the compound. Alternatively if the metal has only two possible charges, the ions can be named using the Latin name of the element with either "ic" as an ending for the higher charge, or "ous" for the lower charge.

Example #1

Example #2

Iron II chloride (or ferrous chloride)

Iron III chloride (or ferric chloride)

Fe⁺² Cl^-1

Fe⁺³ Cl^-1

FeCl₂

FeCl₃

Radicals, being groups of atoms, are treated exactly the same as elements. Their identity is kept sacred through the use of parentheses when the subscript is greater than 1.

Example

Calcium nitrate

Ca⁺² NO₃^-1

Right: Ca(NO₃)₂

Wrong: CaNO₃₂

You may be thinking, “There has to be a better way!” You’re right. Well, maybe not better, but certainly faster.

The Big Switch

The method works like this:

Example #1

Example #2

Sodium chloride

aluminum bromide

Na Cl

Al Br

Na⁺¹ Cl^-1

Al⁺³ Br^-1

Na⁺¹ Cl^-1

Al⁺³ Br^-1

NaCl

AlBr₃

Example #3

Example #4

ammonium sulfate

Iron III carbonate

NH₄⁺¹ SO₄^-2

Fe⁺³ CO₃^-2

NH₄⁺¹ SO₄^-2

Fe⁺³ CO₃^-2

(NH₄)₂SO₄

Fe₂(CO₃)₃

Don't get Switchitis!

Note: Barium oxide

Ba⁺² O^-2

(2) + (-2) already adds to zero.

If you have switchitis you would get Ba₂O₂. This is INCORRECT!! Formulas of ionic compounds are written in the lowest whole number ratios.

Naming Formulas:

Writing the name of an ionic compound is simpler than acids or non-ionics. Simply write the name of the first ion, then the name of the second ion. Ignore the subscripts.

Examples:

Na₂SO₄ sodium sulfate (NH₄)₃PO₄ ammonium phosphate

When the second ion (the negative one) is an element from the table, replace the end of the element’s name with “ide”

Example:

NaCl sodium chloride (not sodium chlorine)

When the first ion (the positive one) is a metal from the chart that can have more than one possible charge, you must indicate the charge in the name. This can be done by using a Roman numeral or by using the Latin name and ending (described above) if the element has only two possible charges.

Examples:

FeBr₂ FeBr₃

Iron II bromide or ferrous bromide iron III bromide or ferric bromide

To determine the charge on the ion, it is USUALLY sufficient to uncross the charges. Just be sure that BOTH charges you get make sense.

Examples:

Fe₂O₃ Cr(OH)₆ CoCl₃

Iron III chromium VI cobalt III

MnO₂

O is NOT –1 so Mn II Mn IV

1. sodium chloride 26. potassium carbonate

2. calcium bromide 27. ammonium sulfate

3. aluminum sulfide 28. ferric oxide (iron III oxide)

4. iron II chloride 29. sodium phosphate

5. potassium iodide 30. aluminum chloride

6. aluminum oxide 31. calcium iodide

7. mercury II oxide 32. potassium fluoride

8. copper I sulfide 33. magnesium nitride

9. calcium sulfide 34. silver nitrate

10. chromium III oxide 35. arsenic V sulfide

11. iron III carbonate 36. barium bromide

12. sodium carbonate 37. barium hydroxide

13. calcium phosphate 38. mercury I hydroxide

14. lithium nitrate 39. lead II oxide

15. potassium phosphate 40. magnesium phosphate

16. ammonium phosphate 41. zinc sulfide

17. barium sulfate 42. potassium nitrate

18. aluminum nitrate 43. iron II acetate

19. lithium carbonate 44. chromium II carbonate

20. sulfur VI oxide 45. ammonium chloride

21. barium phosphate 46. ferrous sulfate (iron II sulfate)

22. tin II hydroxide 47. copper II acetate

23. ammonium carbonate 48. cuprous oxide (copper I oxide)

24. cobalt III bromide 49. hydrogen hydroxide

25. manganese IV oxide 50. magnesium fluoride

Name the following ionic compounds:

1. CaCO₃

2. KCl

3. FeSO₄

4. LiBr

5. MgCl₂

6. FeCl₃

7. Zn₃(PO₄)₂

8. NH₄NO₃

9. Al(OH)₃

10. CuC₂H₃O₂

11. PbSO₃

12. NaClO₃

13. CaC₂O₄

14. Fe₂O₃

15. (NH₄)₃PO₄

16. NaHSO₄

17. Hg₂Cl₂

18. Mg(NO₂)₂

19. CuSO₄

20. NaHCO₃

21. NiBr₃

22. Be(NO₃)₂

23. ZnSO₄

24. AuCl₃

25. KMnO₄