Introduction Lecture 1-02
Naming Inorganic Compounds (Nomenclature)
(Special Tutorial)
If all compounds referred to by a common or trivial name – water,
ammonia, glucose - we would have to learn millions of unrelated
names – impossible.
The systematic method of assigning names to chemicals is often
known as nomenclature.
Compounds formed by carbon and hydrogen and carbon,
hydrogen together with oxygen, nitrogen and a few other
elements called organic compounds.
Compounds that do not fit this description are inorganic
compounds.
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A list of commonly used elements is shown below. Additional
chemical symbols may be found on periodic table of the elements.
Keep in mind that when symbol has two letters in it, the first letter
is always a capital followed by a small case letter.
e.g. The symbol for tin is Sn, not SN or sn or SN
When you write out the name of an element, you do not require a
capital letter at the beginning of the name.
e.g. Sb is antimony not Antimony
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The most commonly used elements are listed below. Watch the spelling.
aluminum
Al
iron(ferrum)
Fe *
antimony(stibium)
Sb
lead(plumbum)
Pb *
argon
Ar
lithium
Li
arsenic
As
magnesium
Mg
barium
Ba
manganese
Mn
bismuth
Bi
mercury(hydrargyrum) Hg
beryllium
Be
neon
Ne
boron
B
nickel
Ni
bromine
Br
nitrogen
N
calcium
Ca
oxygen
O
carbon
C
phosphorus
P
chlorine
Cl
potassium(kalium)
K
chromium
Cr
radium
Ra
copper(cuprum)
Cu *
silver(argentum)
Ag
fluorine
F
sodium(natrium)
Na
gold(aurum)
Au
sulfur
S
helium
He
tin(stannum)
Sn *
hydrogen
H
uranium
U
iodine
I
zinc
Zn
*Names and symbols shown in blue often cause difficulties
* An “*” indicates that the latin name must be used in the “ous – ic” system
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Some common elements are shown below. Do you see a
problem?
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Valence Shell Electrons
Valence shell electrons are those electrons found in outer energy
level of an atom and are only electrons capable of bonding.
Bonding type dependent upon extent bonding electrons are
shared.
Bonding type may be determined by studying Lewis Structures
and electronegativity values.
The most common number of valence shell electrons "involved in
bonding" may be found using this guide. These numbers
correspond to oxidation numbers shown on the periodic table or to
the number of unpaired valence shell electrons in an element.
Group
Valence
IA IIA
+1 +2
IIIB
+3
IVB VB
+4
-3
APSC 131 – Introduction Lecture 1-02 – Naming Chemical Compounds
VIB
-2
VIIB
-1
VIII
0
5
The positive sign indicates that if an ion was formed during
bonding, electrons would be lost by the element and the resulting
ion formed would take on a positive charge.
The negative sign indicates that if an ion was formed during
bonding, electrons would be gained by the element and the
resulting ion formed would take on a negative charge.
The positive and negative charges would result only if ions are
formed. Oxidation numbers give chemists a method of keeping
track of electrons.
When you are unsure of an element’s oxidation number, look it up
on the periodic table.
Example: What are oxidation numbers of F, Ca, S, Fe?
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Binary Compounds
A binary compound is a compound formed from two elements
only. The name of any binary compound ends in "ide".
To name a particular binary compound, the metallic element
(found to the left of the steps on periodic table) is named first.
The non-metallic element (found to the right of the steps on
periodic table) is then named, except that its ending is changed to
"ide".
Example: NaCl KBr -
sodium chloride
potassium bromide
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When writing formulae:
1. For convenience, treat all compounds as ionic compounds,
even though many are covalent.
2. Compounds have no net charge. Therefore, positive and
negative charges on ions have to balance one another.
Example: MgCl2 has one Mg
net charge.
2+
1-
ion and two Cl ions, hence no
3. The positive ion in a compound is written before the negative
ion.
Example: sodium chloride has the formula NaCl
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Write the chemical formula for:
a) potassium chloride
b) sodium oxide
c) aluminum fluoride
d) copper oxide
e) iron chloride
________________________________
________________________________
________________________________
________________________________
________________________________
Write the name of the following formulae:
f) CaO
g) BaI2
h) Rb2O
i) Hg20
j) HgO
________________________________
________________________________
________________________________
________________________________
________________________________
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Notice that d) and e) above have two formulae each. These two
answers are easy to distinguish when looking at the formulae.
However, we must be able to distinguish them by name.
Similarly, i) and j) have two different formulae yet they have the
same name.
How do we eliminate these ambiguities?
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IUPAC SYSTEM
A naming system called the IUPAC system (International Union of
Pure and Applied Chemistry) was developed to eliminate such
difficulties.
If you are naming a chemical compound from a formula, and first
element in the formula has more than one oxidation number, the
oxidation number for this multi-valent element is placed as a
Roman Numeral, in brackets, after name of the element.
This method can be used to name any compound.
copper (I) oxide is
__________________
__________________
Hg3N is
FeCl2 is
__________________
iron (III) sulfide is
__________________
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-OUS -IC SYSTEM
'IUPAC system' is not only system used for naming compounds
containing elements with multiple oxidation numbers.
If bonding is between metal with two oxidation numbers and a
nonmetal, an older system, still in use in naming of such
compounds, is the -ous -ic system.
Where metallic element has only two oxidation numbers, the lower
oxidation form has the ending 'ous' while the higher oxidation form
has the ending 'ic'.
This naming method requires knowing Latin names of some of
elements, namely:
copper
cuprum
iron
ferrum
lead
plumbum
tin
stannum
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Examples:
Cu2O is
_________________
Plumbic sulfide is
_________________
FeCl2 is
_________________
Stannous nitride is
_________________
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PREFIX SYSTEM
Third way of naming compounds is prefix system. This method is
often used when bonding occurs between two non-metals. To use
this method you do not require oxidation numbers but must know
following prefixes.
monoditritetrapentahexaheptaoctanona
deca
1
2
3
4
5
6
7
8
9
10
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When naming, place prefix indicating number of each type of atom
in formula before the name of each element. Second element
again has its ending changed to -'ide'. If the prefix 'mono' appears
in front of first nonmetal, it may be omitted.
Name each of the following. Where applicable, give two names.
1.
2.
3.
4.
5.
6.
7.
8.
9.
ZnS
FeO
Sb2S3
CaCl2
BaO
CuBr2
HgCl2
H2O
PBr3
_____________________________________
_____________________________________
_____________________________________
_____________________________________
_____________________________________
_____________________________________
_____________________________________
_____________________________________
_____________________________________
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Write the formulae for each of the following.
1. sodium chloride
_____________________________
2. calcium bromide
_____________________________
3. ferrous sulfide
_____________________________
4. copper (II) iodide _____________________________
5. cuprous selenide _____________________________
6. manganese (II) oxide____________________________
7. stannic sulfide
_____________________________
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Compounds with Polyatomic Ions:
Not all compounds are binary. This can easily be noticed by
flipping through a chemistry book and noting the names of many
compounds not ending in 'ide'.
Compounds not binary, generally contain a polyatomic ion
consisting of a number of atoms. which hang around as a group.
The group remains unchanged during a chemical reaction, and
has a single oxidation number.
Key to remembering many of polyatomic ions is knowing the five
oxy-acids listed below (and several others which will be shown
to you). They will unlock thousands of chemical formulae to you.
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OXY-ACIDS
chloric acid
nitric acid
sulphuric acid
carbonic acid
phosphoric acid
HClO3
(iodic HIO3, bromic HBrO3)
HNO3
H2SO4 (selenic H2SeO4, telluric H2TeO4)
H2CO3
H3PO4
Several other acids can be easily found by adding and subtracting
oxygen atoms to/from the above oxy-acids. A summary of these
acids is shown below.
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Hypo_ous Acid ous Acid
ic Acid
Per____ic Acid
HClO
HClO2
HClO3
HClO4
___
HNO2
HNO3
_____
___
H2SO3
H2SO4
_____
___
H2CO2
H2CO3
_____
H3PO4
_____
___
H3PO3
<-------- Subtract an O
Add an O -------->
*the acids in blue make up the “home row”
Examples of Acids:
HClO is hypochlorous acid
phosphorous acid is H3PO3
HClO4 is perchloric acid
tellurous acid is H2TeO3
HIO2 is iodous acid
selenic acid is H2SeO4
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Polyatomic anions may be obtained from above acids by removing
H from first part of formula. Oxidation number for polyatomic ion
is equal in number to number of H's found in the acid (the
oxidation number of hydrogen is 1+). A table of the polyatomic
ions obtained from above acids is shown below.
Table of Polyatomic Ions
hypo____ite _______ite
______ate
per_____ate
1
ClO1ClO2 ClO31ClO4111---NO2
NO3
---22---SO3
SO4
---22---CO2
CO3
---33---PO3
PO4
---<------------- SUBTRACT AN O ADD AN O ------------->
* the polyatomic ions in blue make up the “home row”
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Even if polyatomic ion is part of chemical formula, compound must
still be electrically neutral. Charge supplied by polyatomic ion
must balance the total opposite charges.
e.g.
3-
3 Na+ balance PO4 to give us Na3PO4
Write a formula for each of the following:
a) sodium sulphite
b) magnesium carbonate
c) aluminum hypochlorite
Give the name of each of the following:
a) HNO2
b) Ca3(PO3)2
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In addition to the polyatomic ions obtained from the oxy-acids,
there are a number of others commonly found in chemistry.
NAME
FORMULA OF ION
OXIDATION NUMBER
11hydroxide
OH
1+
ammonium
NH4
1+
1acetate
CH3COO (C2H3021-)
11permanganate
MnO4
12chromate
CrO4
22dichromate
Cr2O7
21bicarbonate
HCO3
11bisulfate
HSO4
11cyanide
CN
11thiocyanate
SCN
122oxalate
C2O4
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Write a formula for each of the following:
(a) potassium acetate
(b) ammonium oxalate
Write the name of each of the following:
(a) CuCr2O7
(b) Fe(SCN)3
Suggested Homework
• Read Petrucci 86 – 92 (if needed to improve understanding)
• Handout 1-01. Nomenclature Worksheet (a must to do)
• Handout 1-02. Nomenclature Worksheet Answers
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