Unit 2 – Notes 2B
“Nomenclature”
Naming
Ionic Compounds
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In this unit you will learn about a type of
substance called an “ionic compound”.
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An ionic compound forms when a metallic
element and a non-metallic element combine.
What happens is this:
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Atoms of the metallic element lose electrons
to form positively-charged ions called
“cations”.
 A positive charge is shown as a + or as a
number followed by a +.
 Ex: Na+ Ca 2+, Al 3+
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Atoms of the non-metallic element gain
electrons to form negatively-charged
ions called “anions”.
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A negative charge is shown as a - or as a
number followed by a -.
 Ex: F- S 2-, N 3-
An ion may form after several non-metal
atom joins together with other nonmetal
atoms. This entire group of atoms is
called a “polyatomic ion”.
 Your orange sheet contains a list of the
common polyatomic ions. It includes
one cation and many anions.
 Each of these ions has a distinct name
and a distinct charge.
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EX: NH4+ is called the “ammonium” ion and
CO3 2- is called the “carbonate” ion
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The oppositely-charged ions combine in
a manner so that overall the entire ionic
compound becomes “neutral”: The sum
of the charges of all the ions present in
the compound equals 0.
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You are learning how to create neutral
formulas for ionic compounds in class.
This video explains how to name ionic
compounds.
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Naming binary ionic compounds.
A binary ionic compound contains ions from
only 2 different elements: a metallic
element and a non-metallic element.
 The metallic element (the cation) will always
be found first in a binary ionic compound’s
chemical formula, and the non-metallic
element (the anion) will always be found
second.
 When you name an ionic compound, you
just say the cation’s name followed by the
anion’s name.
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The cation’s name in a binary ionic compound
may be identical to the name of the element it
came from, (as written in the element’s square
on the periodic table).
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This occurs when an element is known to only form
cations that have one particular positive charge.
We’ll look at column 1 metals as an example.
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Metals in column 1 only form 1+ cations; so a
column 1 cation is called by the same name as
the element it formed from.
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Ex: Na+ is called the sodium ion. Li+ is called the
lithium ion. K+ is called the potassium ion. Etc.
Although hydrogen is not a metal, it is still able
to form a cation with only one particular
positive charge! So, H+ is called the hydrogen
ion.
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Note: Hydrogen is a non-metal, and when it
behaves similarly to other non-metals, it forms a 1anion. H- is called the “hydride” ion. You should
memorize this name!
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If a metallic element is known to form cations
whose positive charge is variable, it is then
necessary to specify the charge as a part of
the cation’s name.
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One method is to use a Roman numeral. This
method of nomenclature is known as the “Stock”
system.
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Copper ions that have a 1+ charge are called “copper(I)
ions”.
Copper ions that have a 2+ charge are called “copper(II)
ions.
It is necessary to memorize the Roman numerals in
order to name compounds by their Stock name.
1 = I 2 = II 3 = III 4 = IV 5 = V 6 = VI 7 = VII
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An alternate method, called the “classical”
method, may be used when metals are known
to form 2 common positively-charged ions.
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The root of the element’s name comes first and is
followed by one of 2 suffixes. Latin names are
used when the element symbols on the periodic
table are derived from the element’s latin name.
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-ous is added to indicate the lesser of 2 possible charges.
-ic is added to indicate the higher of 2 possible charges.
Cu+ is referred to by the Stock name,
copper(I); and it is referred to by the classical
name, cuprous
Cu2+ is similarly either referred to as copper(II)
or cupric
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Cations that have 2 variable positive charges
and are named in Latin.
Cu
 Fe
 Sn
 Au
 Hg
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Pb
Cuprum
Ferrum
Stannum
Aurum
Cuprous Cupric
Ferrous Ferric
Stannous Stannic
Aurous Auric
Hydrargyrum Hydrargyrous
Hydrargyric
Plumbum PlumbousPlumbic
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Naming anions.
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In a binary ionic compound, the anion’s name will
be SIMILAR (although not identical) to the name of
the non-metallic element it came from.
An anion from a nonmetallic element is named by
adding the suffix –ide to the “root” of the element’s
name.
These are the anion names you should
memorize from columns 15, 16, and 17:
Nitride, phosphide, arsenide
Oxide, sulfide, selenide, telluride
Fluoride, chloride, bromide, iodide, astatide
Column 1: hydrogen’s anion, H- = hydride.
When you name an ionic compound, you just
say the cation’s name followed by the anion’s
name.
NaCl
= sodium chloride
LiO
= lithiun oxide
Ca3S2
= calcium sulfide
Ba(C2H3O2)2
= barium acetate
(NH4)2(SO4)
= ammonium sulfate
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This is more correctly written as (NH4)2SO4
Notice the “numbers” aren’t part of the names
Whenever the cation is known to exist with a
variable charge, the specific cation should be
indicated as you name the compound. This is
by either using the Stock name or the classical
name.
CuCl = copper(I) chloride or cuprous chloride
CuO = copper(II) oxide or cupric oxide
Fe2S3 = iron(III) sulfide or ferric sulfide
Fe(C2H3O2)2 = iron(II) acetate or ferrous acetate
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Notice that the Roman numerals aren’t gotten
directly from the presence of subscripts.