Chemistry 100
Clark College
Inorganic Nomenclature
In order to efficiently be able to discuss chemicals and reactions, we need to understand a common
system of chemical nomenclature. Nomenclature is crucial as you further your studies in chemistry –
understanding and utilizing proper terminology will help you in the lecture setting, and more
importantly, in the lab. The IUPAC (International Union of Pure and Applied Chemists) system of
nomenclature provides a set of rules for the naming compounds and writing formula. We are going to
learn this system for inorganic compounds.
Note: As we work through nomenclature, it is important that you know the names of elements and ions!
Identifying the Type of Compound
Before naming the compound, we must first classify the compound as an ionic compound or a molecular
compound.
Ionic compounds: Contains one or more metal ions. Exceptions: A molecule is also ionic if it contains
hydrogen ions (H+) or ammonium ions (NH4+).
Molecular compounds: Contains nonmetals only.
Once we have identified the type of compound, we can apply the appropriate rules of writing formula
and naming compounds. We’ll start with ionic compounds.
Ionic Compounds: Writing formulas
For all ionic compounds, the cation is listed before the anion.
Step 1: Determine the charges for each ion.
Step 2: Determine the how many of each ion is needed for charge neutrality.
Check: Is the sum of the positive charges = the sum of negative charges?
Step 3: Reduce the subscripts to give the smallest ratio of whole numbers.
Examples:
NaF, MgI2, K2S, HCl,
What about polyatomic ions? Consider polyatomic ions as a package deal. The package must remain
intact, and the charge applies to the entire package. When you need multiple polyatomic ions to
equalize charge, put the entire package in parentheses, and then indicate the number of ions needed
outside the parentheses.
Examples:
Ca(NO3)2, Li2SO4, (NH4)2O, Mg3(PO4)2
Ionic Compounds: Naming compounds
For all ionic compounds, the name consists of the cation name followed by the anion name.
Type I Ionic Compounds
These compounds are formed from cations that form only one ion, such as group I, II, and II metal ions.
Some additions to this group are compounds that contain hydrogen ions, ammonium ions, and the
transition metal ions silver (Ag+), and zinc (Zn+2).
Cation: takes the name of the element.
Anion: the name of the polyatomic ion, or
take the “base” name of the nonmetal, add -ide
Example:
nitrogen → nitride
Inorganic Nomenclature
chlorine → chloride
NF Su07
oxygen → oxide
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Chemistry 100
Clark College
Type II Ionic Compounds
These compounds are formed from cations that form multiple ions. These cations are typically formed
from transition metals and p-block metals. The naming method is similar, with the addition of the
charge of the cation listed after the element name, in parentheses and in roman numerals.
Examples:
Ion
Cu+1
Cu+2
IUPAC Name
Copper (I)
Copper (II)
Hg2+2
Hg+2
Mercury (I)
Mercury (II)
Sn+2
Sn+4
Tin (II)
Tin (IV)
Cr+3
Chromium (III)
This is polyatomic!
Some examples of Type I and Type II compounds:
Ca(NO3)2
BaCl2
Sn(CO3)2
FePO4
Ammonium sulfide
Lead (II) chloride
Rubidium perchlorate
Iron (III) oxide
Calcium nitrate
Barium chloride
Tin (IV) carbonate
Iron (III) phosphate
(NH4)2S
PbCl2
Rb(ClO4)2
Fe2O3
Molecular Compounds: Naming Binary Compounds
In this course, we will only name binary compounds, or compounds that have two, and only two, types
of nonmetal atoms combined together. Recall that these do not include hydrogen-containing
compounds. Similar to the ionic compounds, the first element retains the name of the element, whereas
the second takes the base and adds –ide. For these compounds, the number of atoms of each element
present is indicated using a greek prefix before the element name (or base), as shown below. The
exception is that the prefix ‘mono’ is not used for the first element.
Greek prefix:
mono-
di-
tri-
tetra-
penta-
hexa-
hepta-
octa-
nona-
deca-
1
2
3
4
5
6
7
8
6
10
Number:
Examples:
Diphosphorus pentoxide
P2O5
Sulfur trichloride
SCl3
Carbon monoxide
CO
Arsenic pentafluoride
AsF5
Inorganic Nomenclature
NF Su07
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Chemistry 100
Clark College
Naming Acids – some special rules
Acids are compounds that form when hydrogen-ion compounds are dissolved in water (signified by an
(aq) following the formula). They fall into two categories for naming: binary acids that contain H+ and
only one other element, and oxo acids that contain H+ and a polyatomic anion that contains oxygen.
Binary Acids
To name a binary acid, replace the –ide ending for the anion and replace it with –ic, and add the prefix
hydro-; “acid” is added as a separate word at the end.
HBr
Hydrogen bromide
HBr (aq)
hydrobromic acid
H2S
Hydrogen sulfide
H2S (aq)
hydrosulfuric acid (this is a deviation)
If the compound is binary (hydrogen and a non-metal), the ide portion from the anion name
changes to ic and a hydro precedes the root name for that non-metal element. In all acids, the
word acid is part of the name – notice the aq after the formula.
Examples formula
HX (g)
HX (aq)
HBr (g)
HBr (aq)
H2S (g)
H2S (aq)
name
Hydrogen rootide (named
like covalent compound)
Hydrorootic acid
hydrogen bromide
(named like covalent cmpd)
hydrobromic acid
hydrogen sulfide (named
like covalent cmpd)
hydrosulfuric acid
Oxo acids
To name an oxo acid, drop the ‘hydrogen’ from the compound name, change the –ate anion ending to
–ic, and add “acid” as a separate work at the end.
HClO4
Hydrogen perchlorate
HClO4 (aq)
perchloric acid
HNO3
Hydrogen nitrate
HNO3 (aq)
nitric acid
If the compound is ternary (hydrogen and a polyatomic ion): and the name ends in ate for the
anion: if the species is a gas, it is named hydrogen polyatomic ion. If the species is aqueous, the
ate from the polyatomic ion changes to ic, the hydro is dropped from the name and the word
acid is added as a suffix.
Inorganic Nomenclature
NF Su07
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Chemistry 100
Clark College
Examples formula
name
H2SO4 (g)
hydrogen sulfate
H2SO4 (aq)
sulfuric acid
More examples:
HClO4 (aq)
anion is perchlorate
perchloric acid
HClO3 (aq)
anion is chlorate
chloric acid
HClO2 (aq)
anion is chlorite
chlorous acid
HClO (aq)
anion is hypochlorite
hypochlorous acid
HCl (aq)
anion is chloride
hydrochloric acid
Some polyatomic ions that we will learn throughout the term!
Formula
Name
Formula
Name
NO3NO2CrO42Cr2O72CNSCNMnO4OHO22NH2SO42SO32PO33-
nitrate
nitrite
chromate
dichromate
cyanide
thiocyanate
permanganate
hydroxide
peroxide
amide
sulfate
sulfite
phosphite
ClO4ClO3ClO2ClOIO4IO3IO2IOBrO4BrO3BrO2BrOCO32-
PO43-
phosphate
HCO3-
hydrogen phosphate
HSO4-
H2PO4-
dihydrogen phosphate
HSO3-
C2H3O2CH3COO-
acetate
acetate
HSNH4+
perchlorate
chlorate
chlorite
hypochlorite
periodate
iodate
iodite
hypoiodite
perbromate
bromate
bromite
hypobromite
carbonate
hydrogen carbonate
or bicarbonate
hydrogen sulfate
or bisulfate
hydrogen sulfite
or bisulfite
hydrogen sulfide
ammonium
HPO42-
Inorganic Nomenclature
NF Su07
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Chemistry 100
Clark College
TABLE 1
COMMON CATIONS AND THEIR OXIDATION NUMBERS
1+
Group IA (1A)
2+
Group IIA (2A)
NH4+ ammonium
Cd2+ cadmium
Cu+ copper (I)
Cu2+ copper (II)
3+
Group IIIA (3A)
4+
Cr3+ chromium (III)
Co2+ cobalt (II)
Co3+ cobalt (III)
Fe2+ iron (II)
Fe3+ iron (III)
Ni2+ nickel (II)
Ni3+ nickel (III)
Pb2+ lead (II)
Pb4+ lead (IV)
Pd2+ palladium (II)
Pd4+ palladium (IV)
Pt2+ platinum (II)
Pt4+ platinum (IV)
Sn2+ tin (II)
Sn4+ tin (IV)
Ag+ silver
Zn2+ zinc
Inorganic Nomenclature
NF Su07
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