Chemical Nomenclature
“Chemical Nomenclature
as we know it is born with
the publication of
Méthode de
nomenclature chimique by
Antoine-Laurent Lavoisier,
Claude-Louis Berthellot,
Antoine de Fourcroy, and
Guyton de Morveau. The
names proposed were
based on the elements
origin or function. (Image
produced courtesy of the
Library & Information
Centre, Royal Society of
Chemistry)”
http://www.rsc.org/chemsoc/timeline//pages/1787.html
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1010
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Barbara Gage
Chemical Nomenclature
• System of rules for naming pure
substances
• Elements – element name used even if
the substance is di- or polyatomic
O2 = oxygen
S8 = sulfur
• Compounds - naming differs depending
on whether a substance is held together
primarily by ionic or covalent bonds.
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Ions…
• Electrons are arranged on levels or
“shells”. Atoms are most stable with 8
electrons on their outermost shell. This
is often referred to as the octet rule.
• Number of electrons on the outer shell
= Group number for elements in Groups
I-VIII A (using the US convention
labeling on periodic table)
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Figure 2.10
The modern periodic table.
US Convention
IUPAC
Convention
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Silberberg, Principles of Chemistry
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Ions…
• To achieve the octet, atoms with more
than 4 electrons on the outer shell will
gain enough electrons to reach 8.
• Cl
Group 7
7 electrons on
outer shell
Cl will gain 1 e- .
• Now #e- = 18 but #p+ = 17 so the
chlorine is an ion with the formula Cl1-.
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Barbara Gage
Ions…
• O Group 6
6 electrons on outer
shell
O will gain 2 e- .
• Now #e- = 10 but #p+ = 8 so the oxygen
is an ion with the formula O2-.
• P
Group 5 5 electrons on outer shell
P will gain 3 e• Now #e- = 18 but #p+ = 15 so the
phosphorus is an ion with the formula P3CHM 1010
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Ions…
• Na Group 1 1 electron on outer shell
O will lose 1 e- to expose the complete
inside shell.
• Now #e- = 10 but #p+ = 11 so the sodium is
an ion with the formula Na1+.
• Mg Group 2 2 electrons on outer shell
Mg will lose 2 e• Now #e- = 10 but #p+ = 12 so the
magnesium is an ion with the formula Mg2+
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--
1+
2+
3+ -Generally metals form cations
and non-metals form anions.
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3- 2- 1-
Binary Ionic Compounds
• Cations (positively charged ions) and
anions (negatively charged ions) will
associate with each other and form a
neutral binary compound to reduce
energy .
• 1 Na+
1 ClNaCl
• 1 Ca2+
1 O2CaO
• 3 K+
1 N3K3N
• 2 Al3+
3 S2Al2S3
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Naming binary ionic compounds
The name of the cation (positively charged ion) is
written first, followed by that of the anion.
The name of the cation is the same as the name
of the metal.
Many metal names end in -ium.
The name of the anion (negatively charged ion)
takes the root of the nonmetal name and adds
the suffix -ide.
Calcium and oxygen form calcium oxide.
Aluminum and sulfur form aluminum sulfide.
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Naming Ionic Binary Compounds
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Naming Binary Ionic Compounds
PROBLEM:
PLAN:
Name the ionic compound formed from the following pairs of
elements:
(a) magnesium and nitrogen
(b) iodine and cadmium
(c) strontium and fluorine
(d) sulfur and potassium
Use the periodic table to decide which element is the metal
and which the nonmetal. The metal (cation) is named first
and we use the -ide suffix on the nonmetal name root.
SOLUTION:
(a) magnesium nitride
(b) cadmium iodide
(c) strontium fluoride
(d) potassium sulfide
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From Silberberg, Principles of Chemistry
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Determining Formulas of Binary Ionic Compounds
PROBLEM:
PLAN:
Write simplest formulas for the compounds named in Sample
Problem 2.5.
Compounds are neutral. We find the smallest number of
each ion which will produce a neutral formula. Place
subscripts to the right of the element symbol.
SOLUTION:
(a) Mg2+ and N3-; three Mg2+(6+) and two N3-(6-); Mg3N2
(b) Cd2+ and I-; one Cd2+(2+) and two I-(2-); CdI2
(c) Sr2+ and F-; one Sr2+(2+) and two F-(2-); SrF2
(d) K+ and S2-; two K+(2+) and one S2- (2-); K2S
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Binary Ionic Compounds
• The “B” group elements may form
cations with more than one charge.
• To specify which cation forms a
compound, a roman numeral equal to the
charge is added to the cation name.
Fe2+ = iron (II) Fe3+ = iron (III)
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Sample Problem 2.7
Determining Names and Formulas of Ionic
Compounds of Elements That Form More Than
One Ion
PROBLEM:
Give the systematic names for the formulas or the formulas
for the names of the following compounds:
(a) tin(II) fluoride
(c) manganese (IV) sulfide
PLAN:
(b) CrI3
(d) CrO3
Compounds are neutral. We find the smallest number of
each ion which will produce a neutral formula. Use
subscripts to the right of the element symbol.
SOLUTION: (a) Tin (II) is Sn2+; fluoride is F-; so the formula is SnF2.
(b) The anion I is iodide(I-); 3I- means that Cr(chromium) is +3.
CrI3 is chromium(III) iodide
(c) Manganese (IV) is Mn2+; oxide is S2-, therefore the
formula is MnS2.
(d) Cr is chromium; the anion O is oxide(2-); the compound is
cobalt (VI) oxide.
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Modified from Silberberg, Principles of Chemistry
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Barbara Gage
Polyatomic Ions
• Some atoms form bonds that hold atoms
together in a structure that has an
overall charge (rather than as a neutral
compound. These ions are called
polyatomic ions.
• CO32- carbonate SO42- sulfate
• Compounds with polyatomic ions are
named with the cation and anion name.
• Na2SO4 – sodium sulfate
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Barbara Gage
Determining Names and Formulas of Ionic
Compounds Containing Polyatomic Ions
PROBLEM:
Give the systematic names or the formula or the formulas
for the names of the following compounds:
(a) Fe(ClO4)2
PLAN:
(b) sodium sulfite
Note that polyatomic ions have an overall charge so when
writing a formula with more than one polyatomic unit, place
the ion in a set of parentheses.
SOLUTION: (a) ClO4 is perchlorate; iron must have a 2+ charge. This is
iron(II) perchlorate.
(b) The anion sulfite is SO32- therefore you need 2 sodiums
per sulfite. The formula is Na2SO3.
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Hydrates
• Some compounds have water molecules
attached as part of their structure.
These are termed hydrates.
• CuSO4. 5H2O
copper (II) sulfate pentahydrate
Numerical Prefixes for Hydrates and Binary Covalent Compounds
Prefix
Prefix
Number
Number
Number
Prefix
1
mono
4
tetra
8
octa
2
di
5
penta
9
nona
3
tri
6
hexa
10
deca
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Binary Acids
• When certain binary gases dissolve in
water they form acids with the same
formula. The name is changed to add –ic
acid to the anion
HCl (g)

HCl (aq)
hydrogen chloride hydrochloric acid
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Binary Acids
•
•
•
•
•
HF (aq)
HCl (aq)
HBr (aq)
HI (aq)
HCN (aq)
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hydrofluoric acid
hydrochloric acid
hydrobromic acid
hydroiodic acid
hydrocyanic acid
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Oxyacids
• Acids containing oxygen; most do not
exist in the same form without water
HNO3
nitric acid
HNO2
nitrous acid
H2SO4
sulfuric acid
H2CO3
carbonic acid
H3PO4
phosphoric acid
HC2H3O2 or CH3COOH acetic acid
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Covalent Binary Compounds
• Non-metals form bonds by sharing
electrons rather than transferring
them.
• The resulting bond is referred to as a
covalent bond.
• The element farthest to the left or
lower on the periodic table is generally
written first. Subscripts are replaced
by numerical prefixes in the name.
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Covalent Binary Compounds
CO2
carbon dioxide
N2 O
dinitrogen oxide
P2S5
diphosphorus pentasulfide
SiCl4
silicon tetrachloride
For compounds where two vowels occur
together when the prefix is added, the
vowel from the prefix can be dropped
(except for iodine).
• N2O5
dinitrogen pentaoxide
•
•
•
•
•
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Naming Binary Covalent Compounds
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Determining Names and Formulas of Binary
Covalent Compounds
PROBLEM:
(a) What is the formula of carbon disulfide?
(b) What is the name of PCl5?
SOLUTION: (a) Carbon is C, sulfide is sulfur S and di-means 2 - CS2.
(b) P is phosphorus, Cl is chloride, the prefix for 5 is penta-.
Phosphorus pentachloride.
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