Chapter 6
Chemical
Nomenclature
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Section 6.1
Introduction to
Nomenclature
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Nomenclature:
A system of names used in a science.
The key to learning such a system
is to minimize memorization and
develop an understanding of a
systematic procedure for naming
chemical compounds.
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Section 6.2
Formulas of Elements
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Goal 1
Given a name or formula of an element in
Figure 5.9, write the other.
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In Chapter 5 you learned the symbols of 35 elements. In
this chapter you will learn the
chemical formulas of those elements.
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Molecule:
The tiniest independent particle of a pure substance.
For most elements, the smallest independent
particle is a single atom.
Their formula is the elemental symbol.
Examples
Element
Formula
Helium
Lithium
He
Li
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Seven elements form diatomic molecules
under normal conditions
Di- means two
The smallest particle of these elements
is two atoms that are chemically attached
to each other
The chemical formula of a diatomic molecule
is the elemental symbol followed by
a subscript of 2
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7 elements occur in nature
as diatomic (two-atom) molecules:
the formula of hydrogen is H2
the formula of nitrogen is N2
the formula of oxygen is O2
the formula of fluorine is F2
the formula of chlorine is Cl2
the formula of bromine is Br2
the formula of iodine is I2
Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007 Brooks/Cole, a part of the Thomson Corporation.
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Some other elements commonly form polyatomic
(many-atom) molecules. However, their natural
molecular form varies, so we will write their formulas as
if they were monatomic (one-atom) species. This will not
affect calculations involving these elements.
Element
Formula
carbon
phosphorus
sulfur
C
P
S
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He
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Cl2
P or
P4
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S or
S8
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C or
C60
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Section 6.3
Compounds Made from
Two Nonmetals
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Goal 2
Given the name or formula of a binary
molecular compound, write the other.
Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007 Brooks/Cole, a part of the Thomson Corporation.
Goal 3
Given the name or the formula of water, write
the other; given the name or the formula of
ammonia, write the other.
Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007 Brooks/Cole, a part of the Thomson Corporation.
The stair-step line in the periodic table separates
elements on the left that are metals from elements on
the right that are nonmetals. Several elements
bordering on this line are metalloids or semimetals.
Compounds formed by two nonmetals or
a metalloid and a nonmetal
are called binary molecular compounds.
Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007 Brooks/Cole, a part of the Thomson Corporation.
Naming binary molecular compounds:
1. The first word is the name of the first
element in the compound, modified with a
prefix to indicate the number of atoms
of that element in the molecule.
2. The second word is the name of the second
element in the compound, changed to end in
-ide, modified with a prefix to indicate the
number of atoms of that element
in the molecule.
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1
mono-
2
di-
3
tri-
4
tetra-
5
penta-
6
hexa-
7
hepta-
8
octa-
9
nona-
10
deca-
Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007 Brooks/Cole, a part of the Thomson Corporation.
Examples:
Write the name of I2O5.
2 = diI = iodine
first word is diiodine
5 = pentaO = oxygen
change 2nd word to end in -ide = oxide
second word is pentoxide
Answer: diiodine pentoxide
Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007 Brooks/Cole, a part of the Thomson Corporation.
Write the formula of nitrogen trifluoride.
No prefix on first word = mono- is implied: 1
The symbol of nitrogen is N
2nd word prefix tri- = 3
-fluoride is an “-ide modified” fluorine = F
Answer: NF3
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Two important exceptions to the
binary molecular compound
nomenclature rules:
H2O is water
NH3 is ammonia
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Section 6.4
Names and Formulas
of Ions Formed by
One Element
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Goal 4
Given the name or formula of an ion in Figure
6.3, write the other.
Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007 Brooks/Cole, a part of the Thomson Corporation.
Figure 6.3
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Ion:
Charged particle formed when a neutral atom
or molecule loses or gains electrons
Cation:
Positively-charged ion.
Formed when a neutral atom or molecule
loses one or more electrons.
Anion:
Negatively-charged ion.
Formed when a neutral atom or molecule
gains one or more electrons.
Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007 Brooks/Cole, a part of the Thomson Corporation.
Monatomic ion:
Ion formed from a single (mono-) atom
Formula of a monatomic ion:
Elemental symbol followed by superscript
size of charge and sign of charge
(if the size of the charge is 1,
the 1 is omitted)
Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007 Brooks/Cole, a part of the Thomson Corporation.
Name of a monatomic cation:
Name of element,
followed by the word ion
Name of a monatomic anion:
Name of element changed to end in -ide,
followed by the word ion
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The charge on a main-group (U.S. A group) ion
corresponds to its group number:
Group
1A
2A
3A
5A
6A
7A
Charge
1+
2+
3+
3–
2–
1–
Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007 Brooks/Cole, a part of the Thomson Corporation.
Examples:
What is the the formula of sodium ion?
Sodium is in Group 1A, so its ion has a 1+ charge
We write the symbol of the element,
followed by the charge in superscript,
omitting the 1
+
Na
Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007 Brooks/Cole, a part of the Thomson Corporation.
What is are the name and formula of the
ion formed from a sulfur atom?
Sulfur is in Group 6A, so it forms 2– ions;
write the symbol of the element,
followed by the charge in superscript:
2–
S
A monatomic anion is named by changing the name of the
element to end in -ide, followed by the word ion:
sulfide ion
Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007 Brooks/Cole, a part of the Thomson Corporation.
Many transition elements (U.S. B groups)
form multiple ions with different charges
All transition-element ions have a positive charge
To distinguish among the ions, the magnitude
of the charge is included with its name:
Cr2+ is chromium(II) ion
Cr3+ is chromium(III) ion
Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007 Brooks/Cole, a part of the Thomson Corporation.
Three of the transition element ions
almost always occur with only one charge,
so chemists do not write the
magnitude of the charge in their names:
Ni2+ is nickel ion
Zn2+ is zinc ion
Ag+ is silver ion
You must memorize their charges
Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007 Brooks/Cole, a part of the Thomson Corporation.
The mercury(I) ion is a special case:
it is a diatomic (two-atom) ion: Hg22+
It is named as if single atoms existed separately:
mercury(I) ion
Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007 Brooks/Cole, a part of the Thomson Corporation.
Example:
What is the formula of copper(II) ion?
What is the name of Zn2+?
The symbol for copper is Cu
(II) indicates the 2+ ion
Cu2+
The name of Zn is zinc
Zinc has just one common charge,
so its charge is not included in its name
zinc ion
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Section 6.8
Formulas of
Ionic Compounds
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Ionic compound:
A combination of cations and
anions that form a crystalline
solid
Must be electrically neutral
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How to Write the Formula of an Ionic Compound
Write the formula of the cation, followed by the formula
of the anion, omitting the charges
Insert subscripts to show the number of each
ion needed in the formula unit to make the
sum of the charges equal to zero with
the fewest number of ions possible
If only one ion is needed, omit the subscript
If a polyatomic ion is needed more than once, enclose
the formula of the ion in parentheses and place the
subscript after the closing parenthesis
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Examples:
What is the formula of magnesium chloride?
Magnesium ion is in Group 2A/2, so its formula is Mg2+
Chlorine is in Group 7A/17, so chloride ion is Cl–
Two 1– ions are needed to balance the 2+ ion
MgCl2
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Refer to this table for your Polyatomic ions. Some General Chemistry
Courses will require you to memorize most of these. Be prepared to do
that!!!
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What is the formula of aluminum oxide?
Aluminum is in Group 3A/13, so
aluminum ion is Al3+
Oxygen in in Group 6A/16, so
oxide ion is O2–
The least common multiple of 2 and 3 is 6,
so 2 x 3+ balances 3 x 2–
Al2O3
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What is the formula of barium nitrate?
Barium is in Group 2A/2, so
barium ion is Mg2+
The formula of nitric acid is HNO3,
so nitrate ion is what results when the H+ is removed,
so it is a 1– ion, NO3–
Two 1– ions are needed to balance the charge
of the 2+ ion, and to retain the identity of
the nitrate ion, enclose it in parentheses
Ba(NO3)2
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Section 6.9
Names of
Ionic Compounds
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Goal 9
Given the formula of an ionic compound
made up of identifiable ions, write the name of
the compound.
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How to Write the Name of an Ionic Compound
Write the name of the cation
Write the name of the anion
To name an ionic compound containing a metal
that commonly is capable of having more
than one ionic charge, the compound name
includes the charge of that metal
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Examples:
Write the name of the following compound:
Zn(NO3)2
Zinc ion has only one common charge, 2+, so the magnitude
of the charge is not included in its name:
zinc ion
NO3– comes from the memorized acid HNO3, nitric acid
-ic changes to -ate:
nitrate ion
zinc nitrate
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Examples:
Write the name of the following compound:
CoCl2
Cobalt ion has more than one common charge
Chlorine, Cl, is in Group 7A/17, so it forms
a 1– ion that ends in -ide:
chloride ion
Two 1– ions means the positive charge must be 2+:
cobalt(II) ion
cobalt(II) chloride
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Section 6.11
Summary of the
Nomenclature System
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Section 6.12
Common Names
of Chemicals
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