NOMENCLATURE:

NOMENCLATURE:

NAMING OF CHEMICAL COMPOUNDS

Before we can begin to make progress in chemistry, we must master its vocabulary. While there are many thousands of different chemical compounds, there is a very definite system of nomenclature whereby we can name most compounds simply and easily.

We can divide the compounds into two main types:

1. Those which are true binary compounds (that is, contain only two types of elements).

2. Those which contain more than two types of elements.

I. NAMING OF BINARY COMPOUNDS

The names of all compounds containing only two elements end in IDE. Binary compounds may be subdivided into two types:

1. Those whose first element is a metal

2. Those whose first element is a non-metal

In both cases the second element is a non-metal.

1. For binary compounds whose first element is a metal, we use the following system:

[name of first element (metal)] [stem] + [IDE]

The stem is merely an abbreviation for the name of the second element (the non-metal).

Example: Naming the compound NaCl

The symbol Na represents the metallic element sodium.

The symbol Cl represents the non-metallic element chlorine, whose stem is chlor.

Therefore, the name NaCl is sodium chlor+ide or sodium chloride.

Likewise, for the following compounds:

CaO is calcium oxide

CaC₂ is calcium carbide

AlN is aluminum nitride

K₂S is potassium sulfide

HCl is hydrogen chloride

Note that hydrogen is considered as a metal when it is written first in a binary compound.

The stems of the most commonly used elements are indicated in the following table:

Oxygen ox Nitrogen nitr

Chlorine chlor Phosphorus phosph

Carbon carb Fluoride fluor

Iodine iod Bromine brom

Hydrogen hydr Sulfur sulf

There are a few special cases in this system of naming.

The ammonium cation NH₄⁺ is considered as a simple metallic ion, therefore:

NH₄Cl is ammonium chloride

(NH₄)₂S is ammonium sulfide

There are also two anions which are considered to be special cases. The hydroxide (OH^-) and the cyanide (CN^-) are considered as simple negative ions, therefore:

KCN is potassium cyanide

Mg(OH)₂ is magnesium hydroxide

NH₄CN is ammonium cyanide

If the metallic ion exists in two valence states:

The charge is designated by Roman numerals, or

The one with the lower charge has the ending OUS

The one with the higher charge has the ending IC.

For example:

Fe⁺² is iron (II) or ferrous ion

Fe⁺³ is iron (III) or ferric ion

Cu⁺¹ is copper (I) or cuprous ion

Cu⁺² is copper (II) or cupric ion

Hg₂⁺² is mercury (I) or mercurous ion

Hg⁺² is mercury (II) or mercuric ion

Sn⁺² is tin (II) or stannous ion

Sn⁺⁴ is tin (IV) or stannic ion

Pb⁺² is lead (II) or plumbous ion

Pb⁺⁴ is lead (IV) or plumbic ion

These rules apply in the same manner to compounds. For example:

FeCl₂ is iron (II) chloride or ferrous chloride

CuS is copper (II) sulfide or cupric sulfide

Cu₂O is copper (I) oxide or cuprous oxide

HgO is mercury (II) oxide or mercuric oxide

SnO₂ is tin (IV) oxide or stannic oxide

Hg₂Cl₂ is mercury (I) chloride or mercurous chloride

2. For binary compounds whose first element is a non-metal, we use the following system:

[name of first element (non-metal)] [prefix] + [stem] + [IDE]

The stem is the abbreviation for the second element. In addition to the ending, a prefix is used.

The prefix designates how many atoms of the second element are present as follows:

mono = 1

di = 2

tri = 3

tetra = 4

penta = 5

hexa = 6

hepta = 7

Example: Naming the compound CO₂

The symbol C represents the element carbon.

The symbol O represents the element oxygen whose stem is ox.

There are 2 atoms of the second element present, so the prefix is di.

The ending, as with all binary compounds is ide.

Therefore, the name CO₂ is:

[name of first element] [prefix] + [stem] + [ide]

carbon di ox ide = carbon dioxide

Likewise, for the following compounds:

SO₂ is sulfur dioxide

SO₃ is sulfur trioxide

CO is carbon monoxide

CCl₄ is carbon tretrachloride

Cl₂O₇ is dichlorine heptoxide

P₂O₃ is diphosphorus trioxide

P₂O₅ is diphosphorus pentoxide

II. NAMING OF ACIDS DERIVED FROM BINARY COMPOUNDS

For binary compounds with hydrogen as the first element:

Place the term hydro at the front of the stem of the second element

The letters IC at the end of the stem

Add the word ACID.

Therefore:

HCl (hydrogen chloride) is hydrochloric acid

H₂S (hydrogen sulfide) is hydrosulfuric acid

HF (hydrogen fluoride) is hydrofluoric acid

HCN (hydrogen cyanide) is hydrocyanic acid (Remember: cyanide ion is a special case)

III. NAMING OF ACIDS WHOSE NEGATIVE GROUP CONTAINS OXYGEN

The only ones which we are concerned with are the common acids of phosphorus, sulfur, nitrogen, chlorine, and carbon. Learn the common oxyacids, which are:

H₂SO₄ H₃PO₄ HNO₃

sulfuric acid phosphoric acid nitric acid

HClO₃ H₂CO₃

chloric acid carbonic acid

If the acid contains one less oxygen atom than the common one, the ending on the stem is changed from IC to OUS. Examples:

H₂SO₃ H₃PO₃ HNO₂ HClO₂

sulfurous acid phosphorous acid nitrous acid chlorous acid

If the acid contains two less oxygen atoms than the common one, the ending in the stem is changed from IC to OUS and the prefix HYPO is added. Example:

HClO

hypochlorous acid

If the acid contains one more oxygen atom than the common one, the prefix PER is added to the name of the common acid. Example:

HClO₄

perchloric acid

Summary Chart

Naming of Acids Whose Negative Group Contains Oxygen

TWO LESS OXYGEN ATOMS
HClO hypochlorous acid
ONE LESS OXYGEN ATOM
HClO₂ chlorous acid	H₂SO₃ sulfurous acid	H₃PO₃ phosphorous acid	HNO₂ nitrous acid
COMMON ACIDS
HClO₃ chloric acid	H₂SO₄ sulfuric acid	H₃PO₄ phosphoric acid	HNO₃ nitric acid
ONE MORE OXYGEN ATOM
HClO₄ perchloric acid

IV. NAMING OF SALTS CORRESPONDING TO THE OXY-ACIDS

For salts derived from the most common acids (the IC acids):

Change the ending IC on the stem to ATE

Include the positive ion

Examples:

Na₂SO₄ [derived from H₂SO₄ (sulfuric acid)] is sodium sulfate.

KNO₃ [derived from HNO₃ (nitric acid)] is potassium nitrate.

(NH₄)₃PO₄ [derived from H₃PO₄ (phosphoric acid)] is ammonium phosphate.

Ca(ClO₃)₂ [derived from HClO₃ (chloric acid)] is calcium chlorate.

For salts derived from the OUS acids:

Change the OUS ending on the stem to ITE

Include the positive ion

Examples:

K₂SO₃ [derived from H₂SO₃ (sulfurous acid)] is potassium sulfite.

Al(NO₂)₃ [derived from HNO₂ (nitrous acid)] is aluminum nitrite.

KClO₂ [derived from HClO₂ (chlorous acid] is potassium chlorite.

For salts derived from the hypo____ous acids:

Change the OUS ending on the stem to ITE

Include the positive ion prefixed by HYPO

Example:

KClO [derived from HClO (hypochlorous acid)] is potassium hypochlorite.

For salts derived from the per____ic acids:

Change the IC ending on the stem to ATE

Include the positive ion

Example:

KClO₄ [derived from HClO₄ (perchloric acid)] is potassium perchlorate.

V. NAMING OF SALTS CONTAINING MORE THAN ONE POSITIVE ION

1. For salts containing two positive ions, one of which is hydrogen, use the following system:

Give the name of the positive ion other than hydrogen.
Use the prefix bi to indicate the hydrogen ion OR name the hydrogen.
Give the proper name for the negative ion using the above rules.

Examples:

NaHSO₄ is sodium bisulfate or sodium hydrogen sulfate

Ca(HSO₄)₂ is calcium bisulfate or calcium hydrogen sulfate

LiHSO₃ is lithium bisulfite or lithium hydrogen sulfite

NaHCO₃ is sodium bicarbonate or sodium hydrogen carbonate

Mg(HCO₃)₂ is magnesium bicarbonate or magnesium hydrogen carbonate

2. Phosphate salts containing more than one type of positive ion, one of which is hydrogen, use the following system:

Give the name of the first positive ion.
Give the name of the second positive ion, using the prefix mono or di to indicate how many atoms of it are present.
Give the proper name for the negative ion

Examples:

NaH₂PO₄ is sodium dihydrogen phosphate

K₂HPO₄ is potassium monohydrogen phosphate

The more advanced student will find that there are other systems for naming these compounds, but this will be enough at the present time.

ASSIGNMENT -- Name the following compounds:

1. ZnS _______________________________ 26. CuCl₂ _____________________________

2. MgCl₂ _____________________________ 27. PCl₅ _____________________________

3. Ca(ClO₃)₂__________________________ 28. LiNO₂ _____________________________

4. CaSO₄ _____________________________ 29. KH₂PO₄ _____________________________

5. AgNO₃ ____________________________ 30. CuCN _____________________________

6. H₂S _______________________________ 31. KHCO₃ _____________________________

7. CaO _______________________________ 32. NaHSO₃ _____________________________

8. H₂CO₃ _____________________________ 33. Li₂HPO₄ _____________________________

9. Mg₃(PO₄)₂ __________________________ 34. H₃PO₃ _____________________________

10. KCl _______________________________ 35. MgSO₄ _____________________________

11. K₂O _______________________________ 36. Ca(IO₂)₂ _____________________________

12. Al(NO₂)₃ ____________________________ 37. SiO₂ _____________________________

13. MgO _______________________________ 38. CuCl _____________________________

14. SnI₂ _______________________________ 39. KClO₂ _____________________________

15. AsCl₅ ______________________________ 40. CaSO₃ _____________________________

16. CuSO₃ _____________________________ 41. NaBr _____________________________

17. HF ________________________________ 42. P₂O₃ _____________________________

18. FeSO₄ ______________________________43. HClO _____________________________

19. SnCl₄ _______________________________44. NO₂ _____________________________

20. AsCl₃ _____________________________ 45. NaH _____________________________

21. KCN ______________________________46. ZnS _____________________________

22. NH₄OH ____________________________47. Pb(NO₃)₂ _____________________________

23. Fe(ClO₄)₃ ___________________________48. H₂Se _____________________________

24. HNO₂ ______________________________ 49. H₃PO₄ _____________________________

25. CS₂ ________________________________ 50. CaH₂ _____________________________

ASSIGNMENT -- Write the formulas for the following compounds:

51. lithium chloride ________________ 76. strontium carbonate ________________

52. phosphoric acid ________________ 77. calcium nitrate ________________

53. boron trichloride ________________ 78. disulfur dichloride ________________

54. ferric chloride ________________ 79. tin (IV) oxide ________________

55. carbon tetrachloride _______________ 80. sodium bicarbonate ________________

56. silver sulfide ________________ 81. strontium chlorate ________________

57. antimony trichloride _______________ 82. aluminum hydroxide ________________

58. barium carbonate ________________ 83. cadium nitrate ________________

59. iodine monochloride ______________ 84. diphosphorus trioxide ________________

60. aluminum nitride ________________ 85. sodium hydride ________________

61. lead sulfate ____________________ 86. calcium nitride ________________

62. ammonium chloride _______________ 87. sulfur trioxide ________________

63. hydrogen fluoride ________________ 88. aluminum nitrate ________________

64. hydrobromic acid ________________ 89. silver oxide ________________

65. tin (II) bromide _________________ 90. ammonium phosphate ________________

66. cuprous oxide __________________ 91. cupric sulfate ________________

67. calcium bicarbonate ______________ 92. lithium fluoride ________________

68. copper (II) cyanide _______________ 93. sodium sulfate ________________

69. cesium fluoride __________________ 94. radium carbonate ________________

70. zinc phosphate __________________ 95. copper (II) oxide ________________

71. dinitrogen pentoxide ______________ 96. iron (III) sulfate ________________

72. iron (II) sulfate ___________________ 97. magnesium perchlorate _______________

73. bromous acid ____________________ 98. potassium hypochlorite ________________

74. perchloric acid ___________________ 99. lithium hydride ________________

75. potassium cyanide ________________ 100.hydrosulfuric acid ________________