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Chapter Four
Ionic Compounds
Fundamentals of General, Organic & Biological Chemistry
4th Edition
Mohammed Hashmat Ali
Southeast Missouri State University
2003 Prentice Hall, Inc.
Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 2Sodium reacts explosively with water.
© 2003 John Wiley and Sons Publishers
Courtesy OPC Inc.
Demo
Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 3The vigorous reaction of sodium with chlorine.
© 2003 John Wiley and Sons Publishers
Courtesy Ken Karp
Demo
Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 4Common table salt, the product of the reaction of sodium with chlorine.
© 2003 John Wiley and Sons Publishers
Courtesy USDA
Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 5Figure 2.12: Names, symbols, electron structures, and compositions of nuclei of the first 10 elements.
© 2003 John Wiley and Sons Publishers
Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 6
The stability of the noble gases is associated with 8 valence electrons (He has 2).
Ne 2, 8Ar 2, 8, 8Kr 2, 8, 18, 8
Atoms can become more stable by acquiring an octet (8 electrons) in the outer shell.
Octet Rule
Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 7Figure 3.3: The reaction of sodium and chlorine to produce sodium chloride.
© 2003 John Wiley and Sons Publishers
Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 8
The valence electrons are the electrons in the outer shell.
The electrons in the outer shell have the most contact with other atoms and strongly influence the chemical properties of atoms.
Valence Electrons
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Number of Valence Electrons For Group A elements, the number of valence
electrons is the number of electrons in the s and p subshells of the outer shell.
In the electron configuration for phosphorus, there are 5 valence electrons in the s and p subshells with the highest number.
5 valence electrons
P Group 5A 1s22s22p63s23p3
Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 10
Valence Electrons for Groups
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State the number of valence electrons for each.
A. Magnesium
1) 2 2) 6 3) 8
B. Oxygen
1) 2 2) 4 3) 6
C. Potassium
1) 1 2) 2 3) 7
Learning Check
Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 12
State the number of valence electrons for each.
A. Magnesium
1) 2 Group 2A 1s22s22p63s2
B. Oxygen
3) 6 Group 6A 1s22s2 2p4
C. Potassium
1) 1 Group 1A 1s22s22p63s23p64s1
Solution
Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 13
Electron Dot Structure
An electron-dot structure is a convenient way to represent the valence electrons.
For example, the two valence electrons for magnesium are placed as single dots on any two sides of the Mg symbol.
Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 14
Electron-Dot Structures
Dot structures are used for Group A elements. The valence electrons are placed on the sides of
the symbol of an element.
Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 15
A. X is the electron dot formula for
1) Na 2) K 3) Al
B. X is the electron dot formula of
1) B 2) N 3) P
Learning Check
Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 16
A. X is the electron dot formula for
1) Na 2) K
B. X is the electron dot formula of
2) N 3) P
Solution
Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 17
The stability of the noble gases is associated with 8 valence electrons (He has 2).
Ne 2, 8Ar 2, 8, 8Kr 2, 8, 18, 8
Atoms can become more stable by acquiring an octet (8 electrons) in the outer shell.
Octet Rule
Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 18
Fig 3.2 The periodic table
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Ionization Energy
Ionization energy is the energy it takes to remove a valence electron.
Metals have lower ionization energies and nonmetals have higher ionization energies.
Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 20
Halogens: Large ionization energy – electron not easily lost; Large electron affinity – electron easily gained – formation of anion is favored.
Fig 4.1 Relative ionization energies (red) and electron affinities (blue) for elements in the first four rows of the periodic table.
Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 21
Metals acquire octets by losing valence electrons. The loss of electrons converts an atom to an ion that
has the electron configuration of the nearest noble gas.
Metals form positive ions because they have fewer electrons than protons.
Group 1A metals ion 1+
Group 2A metals ion 2+
Group 3A metals ion 3+
Metals Form Positive Ions
Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 22
Give the ionic charge for each ion.
A. 12 p+ and 10 e-
1) 0 2) 2+ 3) 2-
B. 50p+ and 46 e-
1) 2+ 2) 4+ 3) 4-
C. 15 p+ and 18e-
1) 3+ 2) 3- 3) 5-
Learning Check
Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 23
Give the ionic charge for each ion.
A. 12 p+ and 10 e-
2) 2+
B. 50p+ and 46 e-
2) 4+
C. 15 p+ and 18e-
2) 3-
Solution
Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 24
Sodium forms an octet by losing its one valence electron.Na – e Na +
1s22s22p63s1 1s22s22p6 (= Ne)
A positive ion forms with a +1 charge.Sodium atom Sodium ion 11 p+ 11 p+
11 e- 10 e-
0 1 +
Formation of a Sodium Ion, Na+
Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 25
Magnesium forms an octet by losing its two valence electrons. Magnesium atom Magnesium ion
Mg – 2e Mg2+
1s22s22p63s2 1s22s22p6 (= Ne)
A positive ion forms with a +2 charge. 12 p+ 12 p+
12 e- 10 e-
0 2 +
Formation of Mg2+
Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 26
When nonmetals gain electrons to achieve an octet arrangement, they form negative ions.
The ionic charge of a nonmetal is 3-, 2-, or 1-.
Formation of Negative Ions
Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 27
Fluorine forms an octet by adding an electron to its seven valence electrons.
1-
: F + e : F :
1s22s22p5 1s22s22p6 (= Ne)
A negative ion forms with a -1 charge.Fluorine atom Fluoride ion 9 p+ 9 p+
9 e- 10 e-
0 1 –
Formation of a Fluoride Ion, F-
Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 28
Group Number and Ions
The Group number can be used to determine the charge of an ion.
The charge of a positive ion is equal to its Group number.
Group 3A = 3+ The charge of a negative ion is obtained by
subtracting its Group number from 8.
Group 6A = - (8-6) = 2-
Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 29
Examples of Ionic Charges
Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 30
A. How many valence electrons does aluminum have?1) 2e- 2) 3e- 3) 5e-
B. How does aluminum acquire an octet? 1) loses 3e- 2) gains 3e- 3) gains 5e-
C. What is the ionic charge of an aluminum ion?1) 3- 2) 5- 3) 3+
D. The symbol for the aluminum ion is1) Al3+ 2) Al3- 3) Al+
Learning Check
Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 31
A. How many valence electrons does aluminumhave?2) 3e-
B. How does aluminum acquire an octet? 1) loses 3e-
C. What is the ionic charge of an aluminum ion? 3) 3+ D. The symbol for the aluminum ion is
1) Al3+
Solution
Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 32
Chapter 4 Compounds and Their Bonds
4.3 Ionic Compounds4.4 Naming and Writing Ionic Formulas
Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 33
Ionic compounds consist of positive and negative ions.
An ionic bond is an attraction between the positive and negative charges.
In an ionic formula, the total charge of the positive ions is equal to the total charge of the negative ions.
total positive charge = total negative charge
Ionic Compounds
Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 34
The formulas of ionic compounds are determined from the charges on the ions.
atoms ions –
Na + F : Na+ : F : NaF
sodium fluorine sodium fluoride
The overall charge of NaF is zero (0).
(1+ ) + (1-) = 0
Ionic Formulas
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Charge Balance In NaCl The formula does not show the charges of the ions
in the compound. The symbol of the metal is written first, followed by
the symbol of the nonmetal.
Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 36
Charge Balance In MgCl2
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Writing Formulas
Because compounds are electrically neutral, one can determine the formula of a compound this way: The charge on the cation becomes the subscript on the
anion. The charge on the anion becomes the subscript on the
cation. If these subscripts are not in the lowest whole-number
ratio, divide them by the greatest common factor.
Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 38
Write the formula of the ionic compound that forms from Ba2+ and Cl.
Write the symbols of the positive ion and the negative ion. Ba2+ Cl
Balance the charges until the positive charge is equal to the negative charge. Ba2+ Cl two Cl- needed
Cl
Write the formula using subscripts for the number of ions for charge balance. BaCl2
Writing a Formula from Charges
Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 39
Write the correct formula for the ionic compound of
A. Na+ and S2-
1) NaS 2) Na2S 3) NaS2
B. Al3+ and Cl-
1) AlCl3 2) AlCl 3) Al3Cl
C. Mg2+ and N3-
1) MgN 2) Mg2N3 3) Mg3N2
Learning Check
Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 40
A. Na+ and S2-
2) Na2S
B. Al3+ and Cl-
1) AlCl3
C. Mg2+ and N3-
3) Mg3N2
Solution
Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 41
Names of Ions Positive ions are named like the element. Negative ions are named by changing the end of the
element name to –ide.
Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 42
Complete the names of the following ions:
N3 O2 F
_________ __________ _________
P3 S2 Cl
_________ __________ _________
Br
_________
Learning Check
Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 43
N3 O2 F
nitride oxide fluoride
P3 S2 Cl
phosphide sulfide chloride
Br
bromide
Solution
Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 44
The name of a binary ionic compound (two elements) gives the name of the metal ion first and the name of the negative ion second.Examples: NaCl sodium chlorideK2S potassium sulfideCaI2 calcium iodideAl2O3 aluminum oxide
Naming Ionic Compounds with Two Elements
Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 45
Write the names of the following compounds:
1) Na3N ___________
2) KBr ___________
3) Al2S3 ___________
4) MgO ___________
Learning Check
Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 46
Complete the names of the following compounds:
1) Na3N sodium nitride
2) KBr potassium bromide
3) Al2S3 aluminum sulfide
4) MgO magnesium oxide
Solution
Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 47
Most transition elements have two or more positive ions.
Ionic Charges of Transition Metals
Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 48
Summary of Common Ions
Of the transition metals, silver and zinc are important elements that form only one ion.
Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 49
A. The formula for the ionic compound of Na+ and O2- is
1) NaO 2) Na2O 3) NaO2
B. The formula of a compound of aluminum and chlorine is1) Al3Cl 2) AlCl2 3) AlCl3
C. The formula of Fe3+ and O2- is 1) Fe3O2 2) FeO3 3) Fe2O3
Learning Check
Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 50
A. The formula for the ionic compound of Na+ and O2- is
2) Na2O
B. The formula of a compound of aluminum and chlorine is
3) AlCl3
C. The formula of Fe3+ and O2- is
3) Fe2O3
Solution
Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 51
Naming Compounds with Transition Metals
Transition metals with two different ions use a Roman numeral following the name of the metal to indicate ionic charge.
Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 52
Learning Check
Select the correct name for each.A. Fe2S3
1) iron sulfide 2) iron(II) sulfide 3) iron (III) sulfide
B. CuS 1) copper (II) sulfide 2) copper(I) sulfate 3) copper (II) sulfate
Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 53
Solution
Select the correct name for each.A. Fe2S3
3) iron (III) sulfide
B. CuS 1) copper (II) sulfide
Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 54
Learning Check
The correct formula is
A. Copper (I) nitride
1) CuN 2) CuN3 3) Cu3N
B. Lead (IV) oxide
1) PbO2 2) PbO 3) Pb2O4
Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 55
Solution
The correct formula is
A. Copper (I) nitride
3) Cu3N
B. Lead (IV) oxide
1) PbO2
Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 56
Arrhenius acids Produce H+ ions in water.
H2OHCl H+(aq) + Cl– (aq)
Are electrolytes. Have a sour taste. Corrode metals. React with bases to form salts
and water.
Acids
Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 57
Arrhenius bases Produce OH– ions in
water. Taste bitter or chalky. Are electrolytes. Feel soapy and slippery. React with acids to
form salts and water.
Bases
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Names of Acids
Acids with H and one nonmetal are named with the prefix hydro- and end with -ic acid.HCl hydrochloric acid
Acids with H and a polyatomic ion are named by changing the end of an –ate ion to -ic acid and an –ite ion to -ous acid.
HClO3 chloric acid
HClO2 chlorous acid
Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 59
Some Acids and Their Anions
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Name each of the following as acids: A. HBr 1. bromic acid
2. bromous acid 3. hydrobromic acid
B. H2CO3 1. carbonic acid
2. hydrocarbonic acid3. carbonous acid
Learning Check
Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 61
A. HBr 3. hydrobromic acid
The name of an acid with H and one nonmetal begins with the prefix hydro- and ends with -ic acid.
B. H2CO3 1. carbonic acid
An acid with H and a polyatomic ion is named by changing the end of an –ate ion to -ic acid.
Solution
Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 62
Bases with OH- ions are named as the hydroxide of the metal in the formula.
NaOH sodium hydroxide
KOH potassium hydroxide
Ba(OH)2 barium hydroxide
Al(OH)3 aluminum hydroxide
Fe(OH)3 iron (III) hydroxide
Some Common Bases
Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 63
Match the formulas with the names:
A. ___ HNO2 1) hydrochloric acid
B. ___Ca(OH)2 2) sulfuric acid
C. ___H2SO4 3) sodium hydroxide
D. ___HCl 4) nitrous acid
E. ___NaOH 5) calcium hydroxide
Learning Check