Unit 1: Back to the Basics

Section 4: Naming Compounds

* Introduction
* Binary Ionic Compounds - Type I
* Binary Ionic Compounds - Type II
* Polyatomic Ions
* Binary Covalent Compounds
* Acids
* Conclusion

Introduction

The most important aspect of Chemistry is not finding new chemical processes
or to be on the leading edge of technology, but to be able to communicate
this new information to other chemists. Because of this, the scientific
community came up with a set of rules to name compounds so that EVERYBODY
would understand what reaction was taking place.

Binary Ionic Compounds - Type I

Binary ionic compounds means two ions, one that is positive in charge
(cation) and one that is negative in charge (anion) that react to form a
compound. In this case, the rules are:

1. The ion with the positive charge (cation) is always written before the
ion with the negative charge (anion)
2. The first word is the name of the element of which the cation
originally came. (Example: Na+ would be called Sodium)
3. The last word is the name of the element of which the anion originally
came. (Example: Cl- would become chlorine, but the first part of the
word is used and -ide is added to the end, so the last word would be
Chloride.)
4. Put the two words together and that is the name of the compound.
(Example: Na+ and Cl- would become Sodium Chloride.)

Common Type II Cations

Ion Systematic Name Alternate Name

Fe+3 Iron (III) Ferric

Fe+2 Iron (II) Ferrous

Cu+2 Copper (II) Cupric

Cu+ Copper (I) Cuprous

Co+3 Cobalt (III) Cobaltic

Co+2 Cobalt (II) Cobaltous

Sn+4 Tin (IV) Stannic

Sn+2 Tin (II) Stannous

Pb+4 Lead (IV) Plumbic

Pb+2 Lead (II) Plumbic

TRY IT YOURSELF: Examples and Practice Problems

Binary Ionic Compounds - Type II

As defined above, binary ionic compounds occur when two ions of opposite
charge react with each other. The difference between type II and type I,
occurs when ions that have the potential to have different charges react.
Type II occurs when ions with the possibility to have two or more charges
react.

Common Cations and Anions

Cations Anion

Cation Name Anion Name

H+ Hydrogen H- Hydride

Ag+ Silver O-2 Oxide

Li+ Lithium S-2 Sulfide

Al+3 Aluminum N-3 Nitride

Ca+2 Calcium F- Floride

When there is a possibility to have different charges, there are two ways of
determining what the name will be. The oldest version, called the alternate
name, was to use -ic and -ous endings on the end of the elements names to
show what the charges were. -ic was used for the ion with the higher charge
and -ous was used for the ion with the lower charge. This probably makes no
sense, so here is an example. In the table above, Co (Cobalt) can have the
charge of +2 or +3, so Cobaltic is Co+3 and Cobaltous is Co+2. The problem
with this system is the everyone must know all the possible ions for each
element to know which one is the bigger one or the smaller one, so another
method was created. This method is called the systematic name method. (I
like this method better!!) Anyway in parentheses after the name of the
element, a Roman numeral is written that indicates what the charge of the
ion is. Using the example above with Cobalt, Co+3 would be written Cobalt
(III) and Co+2 would be written Cobalt (II).

So if Co+2 were to react with O-2 (Oxygen), it could be written as Cobaltous
Oxide, or Cobalt (II) Oxide. (Remember, the last word ends in -ide.) Below
are a few examples that incorporate both methods.

TRY IT YOURSELF: Examples and Practice Problems

Polyatomic Ions

Polyatomic Ions are ions that contain a number of ions. There is a list of
polyatomic ions below. There is no way to learn how to write their names,
except to commit them to memory. (When you commit them to memory, remember the charges, names, and formulas.)

Common Polyatomic Ions

Ion Name Ion Name

NH4+ Ammonium O2-2 Peroxide

NO2- Nitrite CrO4-2 Chromate

NO3- Nitrate Cr2O7-2 Dichromate

SO3-2 Sulfite MnO4- Permanganate

SO4-2 Sulfate C2H3O2- Acetate

HSO4- Hydrogen Sulfate ClO4- Perchlorate

OH- Hydroxide ClO3- Chlorate

CN- Cyanide ClO2- Chlorite

PO4-3 Phosphate ClO- Hypochlorite

HPO4- Hydrogen Phosphate HCO3- Hydrogen Carbonate

H2PO4- Dihydrogen Phosphate CO3-2 Carbonate

Binary Covalent Compounds

Binary covalent compounds are those that do not involve metals or ions. An
example of the difference between a covalent compound is that CO2 is a
covalent compound, but NaCl is not, because it contains Na+, a metal and an
ion.) Here are the rules for naming a binary covalent compound.

1. The first element in the formula uses the whole name of the element,
much like binary ionic compounds. (Example: In NO, the first word would
be Nitrogen.)
2. The second element in the formula only uses the first half of the word
and -ide is added in place of the removed ending, much like binary
ionic compounds. (Example: In NO, the first part of the second word
would be -oxide.)
3. So the person reading the name can determine what the subscript is on
each element, a prefix is added to show how many of each element are
used. The first word of the formula does not use mono, so CO (Carbon
Monoxide), NOT (Monocarbon Monoxide).

Prefixes in Chemical Names

mono 1

di 2

tri 3

tetra 4

penta 5

hexa 6

hepta 7

octa 8

nona 9

deca 10

TRY IT YOURSELF: Examples and Practice Problems

Acids

Acids will be discussed in depth later in this Text Book, but for
now, acids are defined as any substance with a H+ in it. For example, H+ and
Cl- form HCl, which is an acid. Naming acids depends on whether or not there
is oxygen in the acid. If there is no oxygen, take away the first word,
which is hydrogen, and add hydro- to the beginning of the last word and and
add -ic or sometimes -ric to the last word. For example, HCl, in the binary
ionic compound format would be Hydrogen Chloride, but as an acid it is
Hydrochloric Acid.

If there is oxygen in the anion, then there is another set of rules. This
set of rules involves adding -ic or -ous to the end of the second word, and
taking away the first word, which is hydrogen. If the anion ends in -ate
then -ate is replaced by -ic. If the anion ends in -ite, then the -ite is
replaced by -ous. An example is HNO2 and HNO3. HNO2 is called hydrogen
nitrite by the binary ionic compound rules, and when it is named as an acid
the name is nitrous acid. HNO3 is called hydrogen nitrate by the binary
ionic compound rules, and when it is named as an acid it is called nitric
acid.

TRY IT YOURSELF: Examples and Practice Problems

Conclusion

This particular section contains a lot of important information, and this
information is used over and over and over again. It is very important to
know these rules inside and out. It is also important to know how to write
the chemical name from the chemical formula and vice versa.