Chapter 4 Chapter 4 Compounds and Their BondsCompounds and Their Bonds

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4.1 4.1 Octet Rule and IonsOctet Rule and Ions

An octet• is 8 valence electrons.• is associated with the stability of the noble

gases.

He is stable with 2 valence electrons (duet).

valence electronsHe 2 2

Ne 2, 8 8 Ar 2, 8, 8 8 Kr 2, 8, 14, 8 8

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Ionic and Covalent BondsIonic and Covalent Bonds

Atoms that are not noble gases form octets

• to become more stable.

• by losing, gaining, or sharing valence electrons.

• by forming ionic bonds or covalent bonds.

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Metals Form Positive Ions Metals Form Positive Ions (Cations)(Cations)

Metals form positive ions)• by a loss of their valence

electrons.• with the electron configuration

of the nearest noble gas.• that have fewer electrons than

protons. • Called cations

Group 1A metals ion 1+

Group 2A metals ion 2+

Group 3A metals ion 3+

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Formation of a Sodium Ion, NaFormation of a Sodium Ion, Na++

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Charge of Sodium Ion, NaCharge of Sodium Ion, Na++

With the loss of its valence electron,

the sodium ion has a 1+ charge.

Na atom Na+ ion 11p+ 11p+

11e- 10e-

0 1+

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2, 8

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Charge of Magnesium Ion, MgCharge of Magnesium Ion, Mg2+2+

With the loss of two valenceelectrons, magnesium forms

apositive ion with a 2+

charge.

Mg atom Mg2+ ion 12p+ 12p+

12e- 10e-

0 2+

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ExamplesExamples

A. The number of valence electrons in aluminum is1) 1e-. 2) 2e-. 3) 3e-.

B. The change in electrons for octet requires a1) loss of 3e-. 2) gain of 3e-. 3) a gain of 5e-.

C. The ionic charge of aluminum is1) 3-. 2) 5-. 3) 3+.

D. The symbol for the aluminum ion is1) Al3+. 2) Al3-. 3) Al+.

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Formation of Negative Ions Formation of Negative Ions (Anions)(Anions)

In ionic compounds, nonmetals in Groups 5A (15), 6A (16) and 7A (17)

• achieve an octet arrangement by gaining electrons.

• form negatively charged ions with 3-, 2-, or 1- charges.

• called anions

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Formation of a Chloride, ClFormation of a Chloride, Cl--

Chlorine achieves an octet by adding an electron to its valence electrons.

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Charge of a Chloride Ion, ClCharge of a Chloride Ion, Cl--

By gaining 1 electron, the chloride ion has a 1- charge.

Chlorine atom, Cl Chloride ion, Cl –

17p+ 17p+

17e- 18e-

0 1–

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Copyright © 2009 by Pearson Education, Inc.

Ionic Charge from Group Ionic Charge from Group NumbersNumbers

• The charge of a positive ion is equal to its Group number.

Group 1A(1) = 1+

Group 2A(2) = 2+

Group 3A(3) = 3+

• The charge of a negative ion is obtained by subtracting 8 or 18 from its Group number.

Group 6A(16) = 6 - 8 = 2-

or 16 - 18 = 2-

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Some Ionic ChargesSome Ionic Charges

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TABLE 4.2

ExamplesExamples

A. The number of valence electrons in phosphorous is1) 4e-. 2) 5e-. 3) 8e-.

B. The change in electrons for octet requires a1) loss of 2e-. 2) gain of 2e-. 3) a gain of 3e-.

C. The ionic charge of sulfur is

1) 2+. 2) 3-. 3) 4-.

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4.24.2 Ionic CompoundsIonic Compounds

Ionic compounds

• consist of positive and negative ions.

• have attractions called ionic bonds between positively and negatively charged ions.

• have high melting and boiling points.

• are solid at room temperature.

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Sodium chloride or “table salt” is an example of an ionic compound.

Ionic FormulasIonic Formulas

An ionic formula

• consists of positively and negatively charged ions.

• is neutral.

• has charge balance. total positive charge = total negative

charge

The symbol of the metal is written first, followed by the symbol of the nonmetal.

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Charge Balance for NaCl, “Salt”Charge Balance for NaCl, “Salt”

In NaCl,

• a Na atom loses its valence electron. • a Cl atom gains an electron.• the symbol of the metal is written first,

followed by the symbol of the nonmetal.

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Charge Balance in MgCl2Charge Balance in MgCl2

In MgCl2,

• a Mg atom loses 2 valence electrons.

• two Cl atoms each

gain 1 electron.

• subscripts indicate the number of ions needed to give charge balance.

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Charge Balance in NaCharge Balance in Na22SS

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In Na2S,

• two Na atoms lose 1 valence electron each.

• one S atom gains 2 electrons.

• subscripts show the number of ions needed to give charge balance.

Writing Ionic Formulas from Writing Ionic Formulas from ChargesCharges

Charge balance is used to write the formula for

sodium nitride, a compound containing Na+ and N3−.

Na+

3 Na+ + N3− = Na3N

Na+

3(+1) + 1(3-) = 0

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Formula from Ionic ChargesFormula from Ionic Charges

Write the ionic formula of the compound with Ba2+ and Cl.

• Write the symbols of the ions.

Ba2+ Cl • Balance the charges.

Ba2+ Cl two Cl- needed Cl

• Write the ionic formula using a subscript 2 for

two chloride ions.

BaCl221

ExamplesExamples

Select the correct formula for each of the following ionic compounds.

A. Na+ and O2-

1) NaO 2) Na2O 3) NaO2

B. Mg2+ and Cl-

1) MgCl2 2) MgCl 3) Mg2Cl

C. Al3+ and O2-

1) AlO 2) Al2O3 3) Al3O2

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Naming Ionic Compounds with Two ElementsNaming Ionic Compounds with Two Elements

To name a compound that contains two elements,

• identify the cation and anion.

• name the cation first, followed by the name of the anion with an –ide ending.

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4.3 Naming and Writing Ionic Formulas

Cation anion

-Metal loses e--appears at the beginning-Keep the original name

- nonmetal gains e-- follow af ter metal/cation-change ending to -ide

ExamplesExamples

Complete the names of the following ions: Ca2+ Al3+ Li+

_________ __________ _________

N3 Se2 F

_________ __________ _________

P3 S2 Br

_________ __________ _________

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Examples of Ionic Compounds with Examples of Ionic Compounds with Two ElementsTwo Elements

Formula Ions Name

cation anion

NaCl Na+ Cl- sodium chloride

K2S K+ S2- potassium sulfide

MgO Mg2+ O2- magnesium oxide

CaI2 Ca2+ I- calcium iodide

Al2O3 Al3+ O2- aluminum oxide

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ExamplesExamples

Write the formulas and names for compounds of the following ions:

Br− S2− N3−

Li+

Al3+

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ExampleExample

Write the formula and names of the following compounds:

1) K+ and Br-

2) Ca2+ and O2-

3) Al3+ and S2-

4) Mg2+ and F-

Transition Metals Form Positive Ions Transition Metals Form Positive Ions

Most transition metals and Group 4 (14) metals form 2 or more positive ions. However, Zn2+, Ag+, and Cd2+ form only one ion.

Metals That Form More Than One Metals That Form More Than One CationCation

The name of metals

with two or more

positive ions

(cations) use a

Roman numeral to

identify ionic

charge.

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Naming FeClNaming FeCl22

To name FeCl2:

1. Determine the charge of the cation using the charge

of the anion (Cl-).Fe ion + 2 Cl- = Fe ion + 2- = 0Fe ion = 2+

2. Name the cation by the element name and add a Roman numeral in parentheses to show its

charge.Fe2+ = iron(II)

3. Write the anion with an ide ending.

FeCl2 = iron(II) chloride

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Naming CrNaming Cr22OO33

To name Cr2O3:1. Determine the charge of cation from the anion

(O2-).2 Cr ions + 3 O2- = 02 Cr ions + 3 (2-) = 0 2 Cr ions - 6 = 02 Cr ions = 6+ Cr ion = 3+ = Cr3+

2. Name the cation by the element name and add a Roman numeral in parentheses to show its charge.

Cr3+ = chromium(III)3. Write the anion with an ide ending. chromium(III) oxide = Cr2O3

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ExamplesExamples

Select the correct name for each.A. Fe2S3

1) iron sulfide 2) iron(II) sulfide 3) iron(III) sulfide

B. CuO 1) copper oxide 2) copper(I) oxide 3) copper(II) oxide

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Writing FormulasWriting Formulas

Write a formula for potassium sulfide.

1. Identify the cation and anion. potassium = K+

sulfide = S2−

2. Balance the charges. K+ S2−

K+

2(1+) + 2(1-) = 0

3. 2 K+ and 1 S2− = K2S

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Writing FormulasWriting Formulas

Write a formula for iron(III) chloride.

1. Identify the cation and anion.

iron (III) = Fe3+ (III = charge of 3+)

chloride = Cl−

2. Balance the charges.

Fe3+ Cl−

Cl− = (3+) + 3(1-) = 0

Cl−

3. 1 Fe3+ and 3 Cl− = FeCl3

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ExamplesExamples

What is the correct formula for each of the following?

A. Copper(I) nitride

1) CuN 2) CuN3 3) Cu3N

B. Lead(IV) oxide

1) PbO2 2) PbO 3) Pb2O4

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4.4 Polyatomic Ions4.4 Polyatomic Ions

A polyatomic ion • is a group of atoms. • has an overall ionic charge.

Some examples of polyatomic ions are

NH4+ ammonium OH− hydroxide

NO3−

nitrate NO2−

nitrite

CO32− carbonate PO4

3− phosphateHCO3

− hydrogen carbonate(bicarbonate)

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Some Compounds with Some Compounds with Polyatomic IonsPolyatomic Ions

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Some Names of Polyatomic Some Names of Polyatomic IonsIons

The names of common polyatomic anions

• end in ate.

NO3− nitrate PO4

3− phosphate

• with one oxygen less end in ite.

NO2− nitrite PO3

3− phosphite

• with hydrogen attached use the prefix hydrogen (or bi).

HCO3− hydrogen carbonate (bicarbonate)

HSO3− hydrogen sulfite (bisulfite)

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Names and Formulas of Common Names and Formulas of Common Polyatomic IonsPolyatomic Ions

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Memorize these ions

Naming Compounds with Naming Compounds with Polyatomic IonsPolyatomic Ions

• The positive ion is named first, followed by the name of the polyatomic ion.

NaNO3 sodium nitrate

K2SO4 potassium sulfate

Fe(HCO3)3 iron(III) bicarbonate

or iron(III) hydrogen carbonate

(NH4)3PO3 ammonium phosphite

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ExamplesExamples

Match each formula with the correct name.

A. MgS 1) magnesium sulfite

MgSO3 2) magnesium sulfate

MgSO4 3) magnesium sulfide

B. Ca(ClO3)2 1) calcium chlorate

CaCl2 2) calcium chlorite

Ca(ClO2)2 3) calcium chloride

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ExamplesExamples

Name each of the following compounds:

A. Mg(NO3)2

B. Cu(ClO3)2

C. PbO2

D. Fe2(SO4)3

E. Ba3(PO3)2

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Writing Formulas with Polyatomic Writing Formulas with Polyatomic IonsIons

The formula of an ionic compound

• containing a polyatomic ion must have a charge balance that equals zero (0).

Na+ and NO3− -> NaNO3

• with two or more polyatomic ions has the polyatomic ions in parentheses.

Mg2+ and 2NO3−

-> Mg(NO3)2

subscript 2 for charge balance

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ExamplesExamples

Select the correct formula for each.

A. aluminum nitrate

1) AlNO3 2) Al(NO)3 3) Al(NO3)3

B. copper(II) nitrate

1) CuNO3 2) Cu(NO3)2 3) Cu2(NO3)

C. iron(III) hydroxide

1) FeOH 2) Fe3OH 3) Fe(OH)3

D. tin(IV) hydroxide

1) Sn(OH)4 2) Sn(OH)2 3) Sn4(OH)

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ExamplesExamples

Write the correct formula for each.

A. potassium bromateB. calcium carbonateC. sodium phosphateD. iron(II) nitrite

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Flowchart for Naming Ionic Flowchart for Naming Ionic CompoundsCompounds

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ExamplesExamples

Name the following compounds:

A. Ca3(PO4)2

B. FeBr3

C. Al2S3

D. NaHCO3

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ExamplesExamples

Write the formulas for the following:

A. iron(II) hydroxide

B. aluminum carbonate

C. copper(II) bromide

D. lithium phosphate

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