Naming Ternary Compounds

Ternary compounds are composed of three elements, one of which is a metal, and two of which are non-metals bonded together in a stable unit called a complex ion, a polyatomic ion,  or a radical.   These complex ions are listed along with their name and charge on the table of common ions on your periodic table.

For example:

The ternary compound NaClO3 is called sodium chlorate, and is composed of the sodium ion (Na+) and the chlorate ion (ClO3-). Complex ions are extremely stable since the non-metals that form them are bonded to each other very strongly and act as though they were a single indivisible particle.  Complex ions tend to organize themselves into what we call families. The naming of members of a family must be understood because all ternary compounds are named according to the name of the complex ion they contain. The most common member of the family is given the -ate ending, and the other members are named "around" this one. For example, the chlorate family is named as follows.

ClO4- is the perchlorate ion (per means "above")
ClO3- is the chlorate ion (most common or abundant)
ClO2- is the chlorite ion
ClO- is the hypochlorite ion (hypo means "below")
Not all families of complex ions have four members. Some have three and some have as few as one. For example the nitrate family consists of only two members, nitrate, and nitrite as follows:
NO3- is the nitrate ion (most abundant)
NO2- is the nitrite ion
The phosphate family also consists of only two members, phosphate and phosphite as follows:
PO43- si the phosphate ion (most abundant)
PO33- is the phosphite ion


A.  Ternary Salts

The rules for naming these compounds are extremely simple. First, name the metal, and then name the complex ion. The name or formula of the complex ion can simply be looked up on the periodic table.  For example:

Na2CO3 is sodium carbonate                     KMnO4 is potassium permanganate

Fe(NO2)2 is Iron(II) nitrite,   (or Ferrous nitrite)

• Try these.  The answers are here.

BaCO3 is                                                  .

Al2(SO4)3 is                                               .

The formula for potassium dichromate is                      .

The formula for mercury(I) hydrogen carbonate is                     .


B.  Ternary Acids  (Oxyacids)

Like all ternary compounds, ternary acids consist of three elements, one of which is hydrogen and the other two are combined in the form of a complex ion. Like binary acids, these compounds are not named as acids unless they are in aqueous solution, as indicated by the symbol (aq). In order to name ternary acids, you must first determine the name of the radical or complex ion in the molecule, and then apply the following rules.

A per  -  ate complex ion is named as a per - ic acid
An           -ate complex ion is named as an       -ic acid
An           -ite complex ion is named as an       -ous acid
A  hypo - ite complex ion is named as a hypo - ous acid


For example:
 

HClO4(aq) contains the perchlorate ion and is named perchloric acid
HClO3(aq) contains the chlorate ion and is named chloric acid
HClO2(aq) contains the chlorite ion and is named chlorous acid
HClO(aq) contains the hypochlorite ion and is named hypochlorous acid
Try these.  The answers are here.
H2CO3(aq) is named                                                                    .

H2CO2(aq) is named                                                                    .

H3PO4(aq) is named                                                                    .

H3PO3(aq) is named                                                                    .

HIO(aq) is named                                                                    .

HBrO4(aq) is named                                                                    .

The formula for Permanganic acid is                                                                    .

The formula for Hypochlorous acid is                                                                    .

C.  Bases

The formula unit of a common base consists of a metallic ion and the hydroxide ion (OH-). Bases are named as hydroxides.
For example:
 

NaOH is sodium hydroxide                        Ca(OH)2 is calcium hydroxide
LiOH is lithium  hydroxide                         Fe(OH)2 is iron(II) hydroxide

Here is more practice. Exercise 5 contains a mixture of binary and ternary compounds.  Make sure you try them all before you look at the answers.  Remember that naming compounds and writing formulas are essential tools in Chemistry.