chapter four ionic compounds fundamentals of general, organic & biological chemistry 4th edition...

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.


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.


Courtesy USDA

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


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


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


Valence Electrons for Groups


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


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


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.


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.


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


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


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


Fig 3.2 The periodic table


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.


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.


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+



Metals Form Positive Ions


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


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


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+


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+


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


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-


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-


Examples of Ionic Charges


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


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


Chapter 4 Compounds and Their Bonds

4.3 Ionic Compounds4.4 Naming and Writing Ionic Formulas


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


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


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.


Charge Balance In MgCl2


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.


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


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


A. Na+ and S2-

2) Na2S

B. Al3+ and Cl-

1) AlCl3

C. Mg2+ and N3-

3) Mg3N2

Solution


Names of Ions Positive ions are named like the element. Negative ions are named by changing the end of the

element name to –ide.


Complete the names of the following ions:

N3 O2 F

_________ __________ _________

P3 S2 Cl

_________ __________ _________

Br

_________

Learning Check


N3 O2 F

nitride oxide fluoride

P3 S2 Cl

phosphide sulfide chloride

Br

bromide

Solution


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


Write the names of the following compounds:

1) Na3N ___________

2) KBr ___________

3) Al2S3 ___________

4) MgO ___________

Learning Check


Complete the names of the following compounds:

1) Na3N sodium nitride

2) KBr potassium bromide

3) Al2S3 aluminum sulfide

4) MgO magnesium oxide

Solution


Most transition elements have two or more positive ions.

Ionic Charges of Transition Metals


Summary of Common Ions

Of the transition metals, silver and zinc are important elements that form only one ion.


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


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


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.


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


Solution

Select the correct name for each.A. Fe2S3

3) iron (III) sulfide

B. CuS 1) copper (II) sulfide


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


Solution

The correct formula is

A. Copper (I) nitride

3) Cu3N

B. Lead (IV) oxide

1) PbO2


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


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


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


Some Acids and Their Anions


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


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


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


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


Match the formulas with the names:A. 4 HNO2 4) nitrous acid

B. 5 Ca(OH)2 5) calcium hydroxide

C. 2 H2SO4 2) sulfuric acid

D. 1 HCl 1) hydrochloric acid

E. 3 NaOH 3) sodium hydroxide

Solution

chapter four ionic compounds fundamentals of general, organic & biological chemistry 4th edition...

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