INTRODUCTORY CHEMISTRY
Fifth Edition by Charles H. Corwin
Chapter
5
Language of
Chemistry
Christopher G. Hamaker, Illinois State University, Normal IL
© 2008, Prentice Hall
IUPAC
• The International Union of Pure and Applied
Chemistry, IUPAC, has set rules for naming
compounds.
• IUPAC set the rules for the naming and
classification of inorganic compounds in 1940.
• These rules, referred to as IUPAC nomenclature
are still in use today.
Chapter 5
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5.1 Classification of Compounds
• Most inorganic compounds do not contain the
element carbon.
– The exceptions are carbon dioxide, CO2, and
carbonates, which contain the ion CO32–.
• There are 3 common classes of inorganic
compounds:
– Ionic (binary ionic, ternary ionic)
– Molecular (covalent)
– Acids (binary and ternary oxyacid)
Chapter 5
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Classification of Compounds
• Below is a flow chart for the classification of
inorganic compounds.
Metal + Nonmetal
Nonmetal + Nonmetal
Chapter 5
HX
4
5.2 Binary Ionic Compounds
• Binary ionic compounds
contain two elements: one metal
and one nonmetal.
– NaCl and AlCl3 are binary ionic
compounds.
Chapter 5
5
Classification of Ions
• Recall, an ion is an atom or group of atoms with a
charge.
• A positively charged ion is called a cation.
• A negatively charged ion is called an anion.
Chapter 5
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Classification of Ions
• Below is a flow chart for the classification of ions.
+
-
Chapter 5
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Cations
• Metal atoms can lose valence electrons and
become positively charged cations.
• Cations are named for the parent atom followed by
the word “ion”
– Na+ is named “sodium ion”
– Al3+ is named “aluminum ion”
• This rule applies for metal that usually form one
ion.
Chapter 5
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Predicting Cation Charges
• Recall that Group 1 metals always form +1 ions
and Group 2 ions always form +2 ions.
• Ag+, Zn2+, and Cd2+ & Al 3+
• All the others are not predictable but you will
have a hint in the name or chemical formula
Chapter 5
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Metals That Form Multiple Ions
• Group “B” metals (and most under the zig-zag line)
• If a metal can form more than one cation, it is named for
the parent, followed by the charge in Roman numerals in
parentheses, followed by the word “ion.”
– Fe2+ is the iron(II) ion
– Fe3+ is the iron(III) ion
• This is called the Stock system of naming cations.
Chapter 5
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Metals That Form Multiple Ions
• Old system uses Latin names (page 128)
– Name of element ending in –ous or –ic
– -ous (lower charge)
– -ic (higher charge)
• See list on your yellow sheet…..”Transiton Metals”
• Example
iron...“ferrum” -> ferrous (Fe+2) or ferric (Fe+3)
tin.. “stannum” -> stannous (Sn+2) or stannic (Sn+4)
lead. “plumbum”->plumbous(Pb+2) or plumbic (Pb+4)
Chapter 5
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Predicting Anion Charges
• Nonmetals gain electrons to form anions in a
predictable fashion.
• Group VIIA/17 atoms gain 1 electron to form –1
ions: F–, Cl–, Br –, and I–.
• Group VIA/16 atoms gain 2 electrons to form –2
ions: O2–, S2–, Se2–, and Te2–.
• Group VA/15 atoms gain 3 electrons to form –3
ions: N3–, P3–, and As3–.
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Monoatomic Anions
• Nonmetals can gain valence electrons and become
negatively charged anions.
• Monoatomic anions are named by dropping the
end of the element name and adding the suffix
–ide.
– Br – is the bromide ion
– O2– is the oxide ion
– N3– is the nitride ion
– S2- is the sulfide ion
Chapter 5
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Ion Charges
• Shown are the elements on the periodic table and
their common charges.
+1
-3
+2
-2 -1
Zn+2
Ag+ Cd+2
Chapter 5
14
Naming Binary Ionic Compounds
• When naming ionic compounds, we combine the
cation and anion name (drop the word “ion”) with
the cation first and the anion second.
• MgO is composed of one magnesium ion and one
oxide ion, therefore the name is magnesium oxide.
• What is the name of Fe2S3?
• Fe3+ is the iron(III) ion and S2– is
the sulfide ion, so the name is
iron (III) sulfide.
Chapter 5
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Formulas for Binary Ionic Compounds
• We can determine formula of a binary ionic
compound from its name.
• What is the formula of iron (III) fluoride?
Cobalt (III) has a +3 charge, Co3+; and fluoride has a
–1 charge, F–.
• Since the total charge must equal zero, the
formula for cobalt (III) fluoride is CoF3.
+3 + (3 X –1) = zero
Chapter 5
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Formulas for Binary Compounds
• We can predict the formula of an ionic compound
based on the formula of a similar compound.
• What is the formula of radium carbonate given
that calcium carbonate is CaCO3?
Radium, Ra, and calcium are both in group 2 and will
have the same ionic charge.
• The formula for radium carbonate is RaCO3.
Chapter 5
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Determining Ionic Charge
• If an ionic compound contains a metal which can
have more than one ionic charge, we must
determine the charge on the ion. The sum total
charge of an ionic compound must equal zero.
• What is the charge on the chromium ion in Cr3N2?
– The charge on an nitride ion is always –3, so we have
a total of 6 negative charges (2 × N3– = 6 negative)
– The sum of the charges on the chromium ions must be
6 positive
– Crx+ + Crx+ + Crx+ = 6 positive  Each Cr is 2+
Chapter 5
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Writing Ionic Formulas
• An ionic compound is composed of positive and
negative ions.
• A formula unit is the simplest representative
particle of an ionic compound.
• A formula unit is neutral, so the total positive
charge must equal the total negative charge in the
formula unit.
• When writing chemical formulas, the cation
(metal) goes first and the anion (nonmetal) goes
second.
Chapter 5
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Formulas of Ionic Compounds
• If the ions in the ionic compound have the same
charge, the formula unit contains one of each ion.
– Na+ and Cl– combine to form NaCl.
– Mg2+ and S2– combine to form MgS.
• If the charges are not equal, we must balance the
positive and negative charges.
– Ca2+ and Cl– combine to form CaCl2.
– Na+ and O2– combine to form Na2O.
Chapter 5
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Crossover Rule
• You can quickly verify that the chemical formula
is written correctly by crossing over the number
on each ion (not sign).
• The charge on the aluminum ion becomes the
subscript for the oxygen, and the charge on the
oxide ion becomes the subscript for the aluminum
ion.
Chapter 5
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Sample Exercise Identifying Ionic and Molecular Compounds
Which of these compounds would you expect to be ionic: N2O,
Na2O, CaCl2, SF4?
Solution
N2O- molecular (nonmetal/ nonmetal)
Na2O- ionic (metal/ nonmetal)
CaCl2 - ionic (metal/ nonmetal)
N2O- molecular (nonmetal/ nonmetal)
Chapter 5
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5.5 Ternary Ionic Compounds
• Ternary ionic compounds contain three
elements, at least one metal and one
nonmetal.
• A group of atoms bound together that has an
overall charge is a polyatomic anion.
– KNO3 and Al(NO3)3 are ternary ionic
compounds.
Chapter 5
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Polyatomic Anions
• Polyatomic anions generally contain one or more
elements combined with oxygen. These anions
are called oxyanions.
• Most oxyanions have names that end in the suffix
-ate.
– SO42– is the sulfate ion
– NO3– is the nitrate ion
Chapter 5
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Naming Oxyanions
• Some oxyanions end in the suffix -ite.
• The oxyanions that end in -ate each have one
more oxygen than the oxyanions than end in -ite.
– NO3- is nitrate, NO2– is the nitrite ion
– SO42- is sulfate, SO32– is the sulfite ion
• Notice that the charge does not change as the
number of oxygen atoms changes.
Chapter 5
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More Polyatomic Anions
• There are two common polyatomic ions that end
in -ide:
– hydroxide, OH– and cyanide, CN–
• There is one common polyatomic ion that has a +
charge and acts like a metal
– Ammonium NH4+
Chapter 5
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Some Common Polyatomic Ions
Chapter 5
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Formulas with Polyatomic Ions
• Follow the same rules as binary ionic compounds;
if the charges are equal, the formula has one of
each ion.
– Mg2+ and SO42– combine to form MgSO4
– K+ and ClO3– combine to form KClO3
• If the charges are not equal, total charge must
equal zero. If you have more than one polyatomic
ion, it is placed in parentheses.
– Al3+ and (CO3)2– combine to form Al2(CO3)3.
Chapter 5
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Naming Ternary Ionic Compounds
• We name ternary ionic compounds like binary ionic
compounds: the cation name followed by the anion
name.
• K2CO3 is named potassium carbonate.
• If we have a metal that can have than one oxidation
state, we have to determine the charge on the metal.
• Co(ClO3)3 is composed of cobalt(III) and chlorate
ions.
cobalt(III) chlorate
Chapter 5
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5.3 Molecular Compounds
• Binary molecular compounds
contain two elements and both
are nonmetals.
– Some examples of binary
molecular compounds are
ammonia (nitrogen trihydride,
NH3; methane, CH4; carbon
dioxide, CO2; and
tetraphosphorous trisulfide,
P4S3.
Chapter 5
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Binary Molecular Compounds
• Binary molecular compounds are composed of
two nonmetal elements.
• A molecule is the simplest representative particle
of a binary molecular compound.
Chapter 5
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Naming Binary Molecular Compounds
• The first element in the compound is named first
and the second element has the suffix -ide.
• The number of atoms of each element must be
indicated by Greek prefixes.
Chapter 5
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Naming Binary Molecular Compounds
• The molecular compound P4S3 is used on match
tips. What is the name of P4S3?
– There are 4 P atoms, use tetra– There are 3 S atoms, use tri– The name for P4S3 is tetraphosphorous trisulfide.
• What is the name for N2O4?
– dinitrogen tetraoxide.
Chapter 5
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An Exception
• There is one exception to the use of the Greek
prefixes when naming binary molecular
compounds.
• If there is only one atom of the first element, the
mono- is not used. The prefix mono- is always
used for the second element.
– CO is carbon monoxide
– XeF6 is xenon hexafluoride
Chapter 5
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Sample Exercise Relating the Names and Formulas of Binary
Molecular Compounds
Name the compounds (a) SO2, (b) PCl5, (c) Cl2O3.
Solution
(a) sulfur dioxide
(b) phosphorus pentachloride
(c) dichlorine trioxide
Give the chemical formulas for (a) silicon tetrabromide, (b)
disulfur dichloride.
(a) SiBr4, (b) S2Cl2
Chapter 5
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5.6 Naming Acids
• An aqueous solution is produced when a
compound dissolves in water. It is indicated by the
symbol (aq).
• An acid is an aqueous solution
containing hydrogen
and one other nonmetal.
HF is an acid.
• If ALL acids begin with “H”, then
the anion must be used to name it
Chapter 5
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Naming Acids
• 3 Rules depending on anion
– “_ide”
– “_ate”
– “_ite”
• If the anion in the acid ends in -ide, change the ending to
-ic acid and add the prefix hydro- .
– HCl (Chloride)  hydrochloric acid
– HBr (bromide)  hydrobromic acid
– HI (iodide)  hydroiodic acid
Chapter 5
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Naming Acids
• If the anion in the acid ends in -ate, change the ending to
-ic acid.
– HNO3 (nitrate)  nitric acid
– HClO3 (chlorate)  chloric acid
– HClO4 (perchlorate)  perchloric acid
• If the anion in the acid ends in -ite, change the ending to
-ous acid.
– HClO: hypochlorous acid
– HClO2: chlorous acid
Chapter 5
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Summary for Naming Acids
Chapter 5
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Sample Exercise 2.14 Relating the Names and Formulas of Acids
Name the acids (a) HCN, (b) HNO3, (c) H2SO4, (d) H2SO3.
Solution
(a) anion CN– (cyanide) hydrocyanic acid.
(b) NO3– (nitrate) nitric acid
(c) SO42– (sulfate) sulfuric acid.
(d) SO32– (sulfite) sulfurous acid
Chapter 5
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