INORGANIC NOMENCLATURE ~ NAMING INORGANIC COMPOUNDS
Every compound has its own CHEMICAL FORMULA and its own NAME. The nomenclature
(naming systems) for IONIC and MOLECULAR compounds are different.
IONIC COMPOUNDS:
These consist of any positive ion (except H+) combined with any negative ion. (If H+ is the
positive ion, the compound is an acid, as we will see later on page 6.)
™ The positive ion (cation) may be a monatomic metal ion (such as Na+) or a polyatomic ion (such as NH4+)
™ The negative ion (anion) may be a monatomic non-metal ion (such as Cl-) or a polyatomic ion (such
as SO42- or NO3-)
When writing formulas for ionic compounds, the net charge of the formula unit must be zero.
(Because the actual formula units are neutral! Oppositely charged ions will come together in a ratio that makes
neutral units of the compound. "Neutrality principle")
Ex: Ca2+ and ClSo the formula is CaCl2
2 Cl- and 1 Ca2+ together have a net charge of zero
Case 1. Binary Ionic compounds: Representative (Type I) Metal + Non-Metal
Examples: KBr potassium bromide
AlCl3 aluminum chloride
Li3N lithium nitride
Note 1: Metal is always first (name unchanged), non-metal second (the ending of the non-metal is
dropped, and the –IDE ending is added).
Note 2: The name does not indicate how many of each ion are in a formula unit.
Exercise: Write formulas for the following cations:
barium ion _Ba2+_ aluminum ion _ Al3+_ potassium ion _ K+_ radium ion _ Ra2+__
Exercise: Write formulas for the following anions:
bromide _Br-_ nitride _ N3-_ iodide _ I-_ oxide _ O2-_ sulfide _ S2-_
Exercise: Name the following:
NaF __sodium fluoride___
MgS __magnesium sulfide_
SrI2 ___strontium iodide__
Ca3N2 __calcium nitride__
K2O __potassium oxide__
Al2O3 __aluminum oxide__
Ba3N2 __barium nitride__
Na3P ___sodium phosphide
Exercise: Give formulas for the following compounds (refer to periodic table only).
cesium phosphide __Cs3P__ calcium iodide _CaI2_ barium fluoride __BaF2__
magnesium nitride __Mg3N2__ aluminum bromide __AlBr3__ sodium selenide _Na2Se
1
Case 2. Binary Ionic Compounds: Type II Metal + Non-Metal
In general, it is NOT possible to use the periodic table to predict what cations (i.e., what the charge
on the cation is) are formed by transition metals or the main group metals that are not in Group 1A
or 2A. Furthermore, unlike the Group 1A and 2A metals, these other metal elements usually form
more than one kind of stable ion. These kinds of metals (and their cations) are called Type II
metals (or cations). You will see that you can figure out the charge on a Type II metal cation in a
given compound from either its formula or from its name.
™ A few metals not in Group 1A or 2A do form only one kind of stable ion. In this class, the
three you need to know are: Al3+, Zn2+, and Ag+. Name ionic compounds with these cations as
in Case 1. Examples: ZnCl2 zinc chloride; Ag2S silver sulfide; AlF3 aluminum fluoride.
™ If the metal forms two ions (Type II), the naming systems are as follows:
Modern (Stock) system: A Roman numeral after the metal name, in parentheses, indicates the
charge on the metal ion. THIS IS THE SYSTEM YOU MUST LEARN IN THIS CLASS!
Examples:
Fe3+ is iron(III)
Sn4+ is tin(IV)
Cu+ is copper(I)
Old system: -ous ending refers to the ion with lower charge.
-ic ending refers to the ion with the higher charge.
Fe2+ ferrous
Fe3+ ferric
Cr2+ chromous
Cu+ cuprous
Cu2+ cupric
Hg2+2 mercurous
Sn2+ stannous
Sn4+ stannic
Pb2+ plumbous
Cr3+ chromic
Hg2+ mercuric
This information is only
included so that if you see these
names elsewhere, you'll have
some idea why. You do not
need to learn these for my
class!!
Pb4+ plumbic
™ Note: The charge on a transition metal ion can be determined from the formula of the
compound it is in by using the charge on the anion and applying the "neutrality
principle" (for a formula unit).
Examples: In FeF2 there are 2 F- ions per formula unit (net charge of -2) so the charge on the
(one) Fe must be +2 (the ion is Fe2+) Name: iron(II) fluoride (or ferrous fluoride)
In Fe2O3 there are 3 O2- ions per formula unit (total charge = -6) so here the ion is
Fe3+ (two of them must add up to +6). Name: iron(III) oxide (or ferric oxide)
™ Note: In this class you will ONLY be required to know/give the modern (Stock) name
™ Exercise: Name the following compounds:
AgCl ____ silver chloride
____
Cu3N ____ copper(I) nitride_____
FeBr3 ____ iron(III) bromide___
Cr2S3 __ chromium(III) sulfide__
Exercise: Give formulas for the following compounds:
chromium(III) oxide _ Cr2O3_ tin(II) fluoride __ SnF2__ iron(III) iodide _ FeI3__
zinc nitride _ Zn3N2__ copper(II) bromide __ CuBr2_ cobalt(II) oxide __ CoO__
2
Case 3. Ionic Compounds with Polyatomic Ions.
Cases 1 and 2 above involve ionic compounds that consist of a metal cation and a non-metal
anion – two types of elements only. These are called binary compounds. Now let us turn to
ionic compounds that are formed from polyatomic ions: (mostly ternary compounds)
™ Note: As before, the charge on a transition metal ion can be determined from the formula of
the compound it is in, if the charge on the anion is known. You simply apply the
"neutrality principle". You must learn the charges (and names and formulas) of the
polyatomic anions!
NOTE: you need not memorize C2O42- (oxalate), although it appears in this handout.
™ As with all ionic compounds, the cation is named first, then the anion:
Examples:
K3PO4
(NH4)2S ammonium sulfide
Zn(NO3)2 zinc nitrate
Fe2(SO4)3
CuCO3
copper(II) carbonate (or cupric carbonate)
potassium phosphate
iron(III) sulfate (or ferric sulfate)
™ Note: In a formula, parentheses ( ) are used around a polyatomic ion only when there are 2
or more of that polyatomic ion in a formula unit (i.e., when the subscript is not 1).
Exercise: Name the following:
(NH4)2O _ ammonium oxide______
Na2SO3 ____ sodium sulfite______
FeC2O4 __ iron(II) oxalate_______
(or ___ferrous oxalate__)
CuNO2 ___ copper(I) nitrite______
(or ___cuprous nitrite___)
Zn3(PO4)2 _ zinc phosphate_______
Ca(HSO4)2 __ calcium hydrogen sulfate__
Sn(NO2)2 __ tin(II) nitrite________
(or ___stannous nitrite___)
or bisulfate
Exercise: Give formulas for the following:
copper(II) nitrate ____ Cu(NO3)2_______
lithium phosphate ______ Li3PO4________
silver carbonate
chromium(II) hydroxide
Cr(OH)2____
Hg(CN)2
____Ag2CO3
barium permanganate
Ba(MnO4)2
mercury(II) cyanide
nickel(II) hydroxide
Ni(OH)2
magnesium bicarbonate ___Mg(HCO3)2
potassium dichromate
K2Cr2O7
aluminum hydrogen sulfate
Al(HSO4)3
3
MOLECULAR COMPOUNDS
When non-metal atoms share electrons with other non-metal atoms, they often form basic units
called molecules. Compounds composed of molecules are thus called molecular compounds.
We shall learn the nomenclature of (only) binary molecular compounds.
Exercise: Define a binary compound ___ A compound made up of only two kinds of atoms (i.e., would
separate chemically into exactly two elements) _
Case 4. Binary Molecular Compounds
™ As with binary ionic compounds, the second atom in the formula gets an –IDE ending
(though it is NOT an ion in these compounds!!! I would not have made this rule!!).
™ Unlike ionic compounds, the number of each atom in each molecule (or formula unit) must
be specified with a prefix (because there is no single ratio of combination dictated by the
"neutrality principle" [atoms are neutral; there are NO IONS in a molecule!]; there are often
many molecular compounds with the same two kinds of atoms [NO2, NO, N2O4, N2O, etc.]).
These are the prefixes you need to know:
1 is mono2 is di3 is tri6 is hexa7 is hepta- 8 is octa-
4 is tetra9 is nona-
5 is penta10 is deca-
™ Note: When there is only one atom of the first element, the mono prefix is omitted.
Examples: NF3 nitrogen trifluoride
P4O10
tetraphosphorus decaoxide
I2S diiodine monosulfide
B2Cl6 diboron hexachloride
Exercise: Name the following:
N2O4
dinitrogen tetroxide
PCl5
phophorus pentachloride
SO2
sulfur dioxide
SO3
sulfur trioxide
CS2
carbon disulfide
Br2O7
dibromine heptoxide
CO
carbon monoxide
P2O3
diphosphorus trioxide
Cl2O
dichlorine monoxide
SF6
sulfur hexafluoride
Exercise: Give formulas for the following:
iodine pentabromide
IBr5
chlorine dibromide ClBr2
oxygen difluoride
OF2
carbon tetrachloride
CCl4
sulfur hexafluoride SF6
silicon dioxide
SiO2
iodine heptafluoride
IF7
nitrogen monoxide NO
dinitrogen trioxide N2O3
™ Also: You must remember these three very important common names:
NH3 (ammonia)
CH4 (methane)
H2O (water)
4
Case 5. Diatomic Molecular Elements
Several common non-metal elements have basic units that are diatomic molecules. The name of
the element refers to the diatomic molecular element. For example, “hydrogen” refers to H2 and
“oxygen” refers to O2. (If we mean the atom, we say atomic hydrogen or atomic oxygen). The
common diatomic elements are the four halogens, oxygen, nitrogen, and hydrogen.
Exercise: List the names and formulas of the 7 elements whose basic units are diatomic molecules:
hydrogen (H2), nitrogen (N2), oxygen (O2), fluorine (F2), chlorine (Cl2), bromine (Br2),
and iodine (I2)
Exercise: Write both the name and formulas (or symbols) of the gases in the following sentence.
Dry air contains about 79% nitrogen and 21% oxygen, with small amounts of carbon dioxide,
neon, and argon. Polluted air may contain small amounts of sulfur dioxide, sulfur trioxide,
nitrogen dioxide, dinitrogen monoxide, chlorine, ammonia, methane, and carbon monoxide.
nitrogen (N2), oxygen (O2), carbon dioxide (CO2), neon (Ne), argon (Ar), sulfur dioxide
(SO2), sulfur trioxide (SO3), nitrogen dioxide (NO2), dinitrogen monoxide (N2O),
chlorine (Cl2), ammonia (NH3), methane (CH4), and carbon monoxide (CO)
Exercise: Write the name or formula of each compound (or element) in the following paragraph.
Probably the most important element found uncombined in nature is O2. O2 is quite reactive,
forming compounds with the halogens F2, Cl2, Br2 and I2. O2 forms two compounds with H2.
Following the usual rules of nomenclature, the most common oxide of hydrogen, whose
formula is H2O, would be named dihydrogen monoxide. The other oxide of hydrogen is
H2O2. O2 forms a series of compounds with N2, many of which are atmospheric pollutants,
including NO, N2O, NO2, N2O4, N2O5.
O2 (oxygen), F2 (fluorine), Cl2 (chlorine), Br2 (bromine), I2 (iodine), H2 (hydrogen), H2O
(dihydrogen monoxide), H2O2 (dihydrogen dioxide, by following the rules you know,
although that isn't actually the formal name—don't worry about it for now), N2 (nitrogen), NO
(nitrogen monoxide), N2O (dinitrogen monoxide), NO2 (nitrogen dioxide), N2O4
(dinitrogen tetroxide), N2O5 (dinitrogen pentoxide)
5
Case 6. ACIDS
As a group, ACIDS are a somewhat unusual subcategory of molecular compounds. They have
the (seemingly strange) property that when dissolved in water, at least some of the formula units
separate into a hydrogen ion, H+, and an anion. So even though they are molecular compounds,
we can think of them as being like an ionic compound formed from H+ and an anion. Since they
form at least some ions in aqueous solution, they are called "electrolytes" (soluble ionic
compounds are also called "electrolytes" for the same reason). The naming system for acids is
different from that of either ionic or molecular compounds. The key to naming all acids is
knowing the name of the anion from which it is derived.
If the anion does NOT contain oxygen: Add the prefix “hydro” and suffix "-ic" to the root of
the anion name (and add the word "acid").
Ex: HCl. Anion is chloride, root is chlor. Name of acid is hydrochloric acid.
HCN. Anion is cyanide, root is cyan. Name of acid is hydrocyanic acid
If the anion DOES contain oxygen: Look at the ending of the anion name:
If the ending is -"ate", add the suffix "-ic" to the root of the anion (and add the word "acid")
Ex: HNO3. Anion is nitrate, root is nitr. Name of acid is nitric acid.
If the ending is -"ite", add the suffix "-ous" to the root of the anion (and add the word "acid")
Ex: HNO2. Anion is nitrite, root is nitr. Name of acid is nitrous acid.
Some acids, called strong acids, have the property that ALL of their formula units separate into
ions in aqueous solution. These acids are often used in industry and in the laboratory. You must
learn the names and formulas of the six common strong acids:
HCl
H2SO4
HNO3
hydrochloric acid
sulfuric acid
nitric acid
HBr hydrobromic acid
HI
hydroiodic acid
HClO4 perchloric acid
Other acids, called weak acids, have the property that only a few percent or less of their
dissolved formula units separate into ions—most of the formula units remain as intact molecules
in aqueous solution. You need not memorize which acids are weak acids! Why not? You can
use deductive reasoning here! If an acid is not one of the six strong ones that you memorized
above, then it must be weak!! Several common weak acids are:
HC2H3O2
H3PO4
H2CO3
H2C2O4
acetic acid
phosphoric acid
carbonic acid
oxalic acid
Exercise: Write the formulas for the underlined acids in the following paragraph:
In industry, hydrochloric acid is known as muriatic acid and is used in concrete work.
Since sulfuric acid is used in automobile batteries, it is commonly called battery acid.
Nitric acid is probably the most common oxidizing agent used in laboratories. Acetic
acid is the acid in vinegar. Phosphoric acid and carbonic acid are added to soft drinks to
provide a pleasantly tart taste. Oxalic acid is found in many plants, including rhubarb
and spinach. A high concentration of this acid is toxic.
HCl (hydrochloric acid); H2SO4 (sulfuric acid); HNO3 (nitric acid); HC2H3O2 (acetic acid);
H3PO4 (phosphoric acid); H2CO3 (carbonic acid); H2C2O4 (oxalic acid)
6
Exercises for Further Practice
Name the following (HINT: You must first decide whether or not the substance is an ionic
compound, a molecular compound (that is not an acid), an acid, or a molecular element):
Na2SO4
sodium sulfate
P2O5
diphosphorus pentoxide
Br2
bromine
BaCO3
barium carbonate
Fe(NO3)2
iron(II) nitrate
PbO2
lead(IV) oxide
SiCl4
silicon tetrachloride
AgClO
silver hypochlorite
(NH4)2C2O4
ammonium oxalate
HNO3
nitric acid
CuCrO4
copper(II) chromate
PbCr2O7
lead(II) dichromate
SeI2
selenium diiodide
CuHPO4
copper(II) hydrogen phosphate
SF4
sulfur tetrafluoride
HgCl2
mercury(II) chloride
Br2O
dibromine monoxide
KClO
potassium hypochlorite
Sn(ClO3)2
tin(II) chlorate
NaH2PO4
sodium dihydrogen phosphate
(or copper(II) biphosphate)_
7
Give Formulas for the Following:
zinc phosphate
Zn3(PO4)2
tin(II) hydroxide
Sn(OH)2
ammonium nitrite
NH4NO2
copper(II) acetate
Cu(C2H3O2)2
lithium sulfite
Li2SO3
silver dichromate
Ag2Cr2O7
sulfur trioxide
SO3
sulfuric acid
H2SO4
nickel(II) chlorate
Ni(ClO3)2
chromium(III) bromide
iron(III) chromate
Fe2(CrO4)3
bromine
Br2
strontium nitrate
Sr(NO3)2
iron(II) hydroxide
Fe(OH)2
calcium carbonate
CaCO3
ammonium sulfite
(NH4)2SO3
copper(II) phosphide Cu3P2
lead(IV) sulfide
PbS2
lead(IV) acetate
potassium dichromate
K2Cr2O7
Pb(C2H3O2)4
CrBr3
titanium(IV) chloride
TiCl4
chromium(II) oxide
CrO
diboron hexafluoride
B2F6
cobalt(II) bromide
CoBr2
aluminum dihydrogen phosphate _Al(H2PO4)3
magnesium carbonate
MgCO3
strontium sulfite
SrSO3
oxygen difluoride
OF2
phosphoric acid
H3PO4
nitrogen
N2
calcium hydroxide
Ca(OH)2
ammonium oxalate
(NH4)2C2O4
sodium hypochlorite NaClO (or NaOCl)
magnesium nitrate
Mg(NO3)2
iron(III) cyanide
silver phosphate
Ag3PO4
iron(II) hydrogen sulfate
Fe(HSO4)2
carbonic acid
H2CO3
gold(III) bromide
AuBr3
Fe(CN)3
potassium permanganate
zinc sulfide
KMnO4
ZnS
lead(II) hydrogen carbonate Pb(HCO3)2
8