Chem 1405 Naming Ionic Compounds Notes

Naming Ionic Compounds

An ionic compound contains ions but are electrically neutral. When the metal lost electrons, it
forms a positively charge ion called a cation . The non-metal, instead, gains electrons and becomes a
negatively charge ion called anion . Being neutral means that the respective cation and anion charges
must cancel.

For example, NaCl contains sodium ions (Na+) with a positive one charge and chloride ions (Cl-) with a
negative one charge giving the NaCl, a net zero charge. When writing ionic compound's chemical
formulas, the metal chemical symbol is written first and then the non-metal. The charges of the
corresponding cations and anions in the formula are not shown.

Let’s consider the ionic compound with formula BaCl2. Is this a neutral ionic compound?
Ba is the symbol for the element Barium in group 2. It makes a cation with a 2 + charge and chlorine make
an anion with 1- charge. If you put together one Ba2+ and one Cl-1, the net charge will be 1+. See below. To
balance the charges, we need two Cl- ions . We use subscripts to balance the charges in a formula.
IAgain, look below and notice how having two Cl- ions produces a formula that is neutral.

Ba2+ + Cl- ------> BaCl
+
2 + 1- = 1+ net charge

(Cation) + (Anion)



Ba2+ + 2 Cl- -------> BaCl2

2+ + 2 (1-) = 0 net charge

(Cation) + (Anion)

So, the answer for the above question is YES. The only correct formula for a compound made of barium
and chlorine is BaCl2.

We refer to the ionic compounds as binary ionic compounds if they contain two elements.
Ionic compounds are classified as Type I binary ionic compound and as Type II binary ionic compounds.
When the metal is from Group 1, Group 2, Al3+, Zn2+, Ag+, and Cd2+ that combines with a non-metal, we
classify the ionic compound as Type I. The metal in an ionic compound always has a fixed charge to be
considered as type I.

The steps to name Type I ionic compounds are as follows:

1. Identify the cation and the anion.

2. Name first the metal (cation) using the name of the neutral element

3. Name the anion by changing the ending of the element's name to the suffix -ide
Table 1 Type I Ionic Compounds

Compound Cation Anion Cation Anion Compound's Name

, Formula Name Name

LiCl Li+ Cl- Lithium chloride Lithium chloride
CaF2 Ca2+ F- Calcium fluoride Calcium fluoride
AgBr Ag+ Br- Silver bromide Silver bromide

Type II binary ionic compounds are made of the same combination of metal and non-metal but on this
one the metal is a transition metal. Transition metals have two or more ionic forms.

For example , iron (Fe) has two common ions Fe2+ and Fe3+. When naming this type of ionic
compounds, the charge of the ion must be specified using roman numbers. (Review how to write
roman numbers)
Table 2 Type II Ionic Compounds

Compound Cation Roman Cation Anion Compound's Name
Number Name Name
Formula
FeCl2 Fe2+ (II) Iron(II) chloride Iron(II) chloride

FeF3 Fe3+ (III) Iron(III) fluoride Iron(III) fluoride
SnI4 Sn4+ (IV) Tin(IV) iodide Tin(IV) iodide

When ask to name a type II ionic compound, first, determine the charge of the metal by looking at the
charge of the anion and its subscript. Don’t forget to consider the neutrality of the ionic compound.

In FeCl2, Cl has a negative one charge, but the formula shows two chloride ions (overall charge= -2). To
have a neutral compound, the iron ion must have a 2+ charge, since we have only one present in this
compound. The Fe: Cl ratio is 1:2 which makes it a neutral type II ionic compound.

Summary of the rules is seen below.