Name ______Naming Ionic Compounds

Ionic compounds are generally composed of a metal and a nonmetal. Formulas for ionic compounds are always written using the lowest whole number ratios of the cation (positive ion) and anion (negative ion).

Ionic compounds are named by first naming the cation and then the anion. For monatomic cations with only one possible positive charge (elements in group 1, 2, 3 and Al3+, see oxidation numbers on the Periodic Table), simply name the element of the cation, i.e. Na+ is the sodium ion. For monoatomic anions (nonmetals), the negative charges typically are the same as the number of electrons required to obtain a Noble Gas electronic configuration. To name a monoatomic anion, take the root of the elements name and add the suffix –ide, i.e. Cl- is the chloride ion. Therefore, to name a simple binary ionic compound such as NaCl, name the cation and then the anion ending in –ide, i.e. sodium chloride. In some cases the cation can have more than one possible charge (usually a d-block metal). It is therefore necessary to use the so-called “stock naming system” by indicating the charge of the cation using a Roman numeral after the cation’s name. For example, Fe2O3 is named iron (III) oxide, whereas FeO is iron (II) oxide. In some cases, the ionic compound will contain polyatomic ions. To name these compounds, again simply name the cation and then the anion. Table 1 contains a list of cations and anions, along with their names. These ions can be used to complete the following.

Table 1. Formulas and Names of various selected cations and anions.

Formula / Name / Formula / Name
NH4+ / Ammonium ion / F- / Fluoride ion
Li+ / Lithium ion / Cl- / Chloride ion
Na+ / Sodium ion / Br- / Bromide ion
K+ / Potassium ion / I- / Iodide ion
Mg2+ / Magnesium ion / O2- / Oxide ion
Ca2+ / Calcium ion / S2- / Sulfide ion
Sr2+ / Strontium ion / N3- / Nitride ion
Sc3+ / Scandium ion / C4- / Carbide ion
Cr2+ / Chromium (II) ion / NO3- / Nitrate ion
Cr3+ / Chromium (III) ion / NO2- / Nitrite ion
Cr6+ / Chromium (VI) ion / CO32- / Carbonate ion
Fe2+ / Iron (II) ion / SO42- / Sulfate ion
Fe3+ / Iron (III) ion / SO32- / Sulfite ion
Mn2+ / Manganese (II) ion / PO43- / Phosphate ion
Mn3+ / Manganese (III) ion / PO33- / Phosphite ion
Cu+ / Copper (I) ion / ClO- / Hypochlorite ion
Cu2+ / Copper (II) ion / ClO2- / Chlorite ion
Pb2+ / Lead (II) ion / ClO3- / Chlorate ion
Zn2+ / Zinc ion / ClO4- / Perchlorate ion
Al3+ / Aluminium ion / OH- / Hydroxide ion

Fill in the blank spaces of the following table.

Formula / Cation / Anion / Name of ionic compound
KCl
Ca2+ / CO32-
Iron (II) sulfate
Fe2(SO4)3
Mg2+ / Cl-
Chromium (III) Chloride
Zn3(PO4)2
Al3+ / OH-
ammonium nitrate
(NH4)2SO4
Na+ / F-
Copper (II) sulfate
Ca(NO3)2
Zn2+ / N3-

Answers

Formula / Cation / Anion / Name of ionic compound
KCl / K+ / Cl- / Potassium chloride
CaCO3 / Ca2+ / CO32- / Calcium carbonate
FeSO4 / Fe2+ / SO42- / Iron (II) sulfate
Fe2(SO4)3 / Fe3+ / SO42- / Iron (III) sulfate
MgCl2 / Mg2+ / Cl- / Magnesium chloride
CrCl3 / Cr3+ / Cl- / Chromium (III) Chloride
Zn3(PO4)2 / Zn2+ / PO43- / Zinc phosphate
Al(OH)3 / Al3+ / OH- / Aluminum hydroxide
NH4NO3 / NH4+ / NO3- / ammonium nitrate
(NH4)2SO4 / NH4+ / SO42- / Ammonium sulfate
NaF / Na+ / F- / Sodium fluoride
CuSO4 / Cu2+ / SO42- / Copper (II) sulfate
Ca(NO3)2 / Ca2+ / NO3- / Calcium nitrate
Zn3N2 / Zn2+ / N3- / Zinc nitride

© Van Der Sluys, 2004