WEEK TWO -- CHAPTER 5: Chemical Formulas and Names

This chapter will concentrate on naming of chemical compounds. Different types of compounds (such as molecular or ionic compounds or acids) have slightly different rules of naming or "nomenclature". It will be important that you know the element names and ion names and charges, in order to be able to name compounds. Until you become familiar with the names and charges, keep the common ion table from chapter 4 handy when you work problems there is a review list at the end of this chapter). We will learn the systematic names of compounds, however, many compounds also have "common names" by which they are known.

LEARNING OBJECTIVES:

  1. Ionic Compounds
    1. Formulas
    2. Names
  2. Molecular Compounds
    1. Formulas
    2. Names
  3. Acids
    1. Binary Acids
    2. Oxyacids 

IONIC COMPOUNDS:
Remember, ionic compounds are:

We can further categorize ionic compounds into either simple binary ionic compounds or ionic compounds with polyatomic ions

Binary Ionic Compounds: both the cation and the anion in the compound are derived from a single element which has lost or gained one or more electrons. Some examples are:

                   Na+       Cl-       Ca2+      O2-      H+  

Ionic Compounds with polyatomic ions: the cation and/or the anion is formed from a grouping of elements and that grouping is either positively or negatively charged. Some examples are: 

                  CO32-       PO43-       NH4+        SO42-

Whether the compounds are simple binary or compounds with polyatomic ions, the rules for naming are much the same.

Some elements can form ions with different charges. This is particularly common in the transition metals (the B Group metals). Some examples are: 

                 Cu+       Cu2+      Fe2+       Fe3+

Naming ionic compounds in which these types of ions occur, is only slightly different than for simple binary compounds with ions which have only a single charge. First a summary of cation and anion charges and names and then the nomenclature rules! 

Summary of Predicting Ion Charges:

Group 1A elements (metals) always form +1 cations
Group 2A elements (metals) always form +2 cations
Group 6A elements (non-metals) generally form -2 anions
Group 7A elements (non-metals) generally form -1 anions
H generally forms a +1 cation

Summary of Naming Ions:

Ion

Name

 

Ion

Name

NO3-

nitrate ion

 

ClO-

hypochlorite ion

NO2-

nitrite ion

 

ClO2-

chlorite ion

SO42-

sulfate ion

 

ClO3-

chlorate ion

SO32-

sulfite ion

 

ClO4-

perchlorate ion

 

Nomenclature Rules for Ionic Compounds:

examples:

Ions Combined

Formula

Name

Na+ and Cl-

NaCl

sodium chloride

Na+ and SO42-

Na2SO4

sodium sulfate

NH4+ and S2-

(NH4)2S

ammonium sulfide

Ba2+ and N3-

Ba3N2

barium nitride

Al3+ and O2-

Al2O3

aluminum oxide

Fe2+ and Cl-

FeCl2

iron(II) chloride

Fe3+ and Cl-

FeCl3

iron(III) chloride

Cu+ and O2-

Cu2O

copper(I) oxide

Cu2+ and O2-

CuO

copper(II) oxide

 

Note that since Na+, sodium, Ba2+, barium, and Al3+, aluminum in the examples above do not have other possible charges (we'll learn why that is in chapter 9), it is not necessary to indicate the charge by roman numerals in parentheses in the name. 

Also note that polyatomic ions are in parentheses when there is more than one unit of that polyatomic ion present and the subscript outside the parentheses indicates the quantity of the polyatomic unit. 

BINARY MOLECULAR COMPOUNDS:

Remember, molecular compounds are:

Prefix

Meaning

 

Formula

Name

mono

one

 

NO

nitrogen monoxide

di

two

 

N2O

dinitrogen oxide

tri

three

 

N2O3

dinitrogen trioxide

tetra

four

 

CCl4

carbon tetrachloride

penta

five

 

SiF4

silicon tetrafluoride

hexa

six

 

SO3

sulfur trioxide

hepta

seven

 

P2O5

diphosphorus pentoxide

octa

eight

 

CO

carbon monoxide

nona

nine

 

CO2

carbon dioxide

 

ACIDS: 

Binary Acids:

Oxyacids:

Problems:

Here is a review of the names and charges of some common ions:

 

COMMON IONS

Positive

Negative

Hydrogen H+ Hydroxide OH-
Sodium Na+ Fluoride F-
Potassium K+ Chloride Cl-
Ammonium NH4+ Bromide Br-
Silver Ag+ Iodide I-
Copper(I) Cu+ Nitrate NO3-
Copper(II) Cu+2 Nitrite NO2-
Barium Ba+2 Perchlorate ClO4-
Calcium Ca+2 Chlorate ClO3-
Zinc Zn+2 Chlorite ClO2-
Nickel Ni+2 Hypochlorite ClO-
Magnesium Mg+2 Acetate C2H3O2-
Cobalt(II) Co+2 Sulfide S-2
Iron(II) Fe+2 Sulfate SO4-2
Manganese(II) Mn+2 Sulfite SO3-2
Mercury(II) Hg+2 Oxide O-2
Aluminum Al+3 Carbonate CO3-2
Iron(III) Fe+3 Phosphate PO4-3
Chromium(III) Cr+3 Bisulfate HSO4-
Cobalt(III) Co+3 Bicarbonate HCO3-
    Cyanide CN-
    Chromate CrO4-2
    Dichromate Cr2O7-2

 

 

 

 

 

Click here to go to Chapter 6 Chemical Reactions and Equations