LecturePLUS Timberlake 1

Chapter 4

Compounds and Their Bonds

4.1 Valence Electrons

4.2 Octet Rule and Ions

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Chemical Bonds

Attraction between two or more atomsInteraction between valence electronsIonic bondsCovalent bonds

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Valence Electrons

Electrons in the highest (outer) electron level

Have most contact with other atoms

Known as valence electrons

Outer shells of noble gases contain 8 valence

electrons (except He = 2)

Example: Ne 2, 8

Ar 2, 8, 8

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Electron Dot Structures

Symbols of atoms with dots to represent the valence-shell electrons

1A 2A 3A 4A 5A 6A 7A 8A

H He:

Li Be B C N O : F :Ne :

Na Mg Al Si P S :Cl :Ar :

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Learning Check

A. X would be the electron dot formula for

1) Na 2) K 3) Al

B. X would be the electron dot formula

1) B 2) N 3) P

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Solution

A. X would be the electron dot formula for

1) Na 2) K

B. X would be the electron dot formula

2) N 3) P

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Octet Rule

An octet in the outer shell makes atoms stable

Electrons are lost, gained or shared to form an octet

Unpaired valence electrons strongly influence bonding

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Formation of Ions from Metals

Ionic compounds result when metals react with nonmetals

Metals lose electrons to match the number of valence

electrons of their nearest noble gas

Positive ions form when the number of electrons are

less than the number of protons

Group 1A metals ion 1+

Group 2A metals ion 2+

• Group 3A metals ion 3+

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Formation of Sodium Ion

Sodium atom Sodium ion

Na – e Na +

2-8-1 2-8 ( = Ne)

11 p+ 11 p+

11 e- 10 e-

0 1+

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Formation of Magnesium Ion

Magnesium atom Magnesium ion

Mg – 2e Mg2+

2-8-2 2-8 (=Ne)

12 p+ 12 p+

12 e- 10 e-

0 2+

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Some Typical Ions with Positive Charges (Cations)

Group 1A Group 2A Group 3A

H+ Mg2+ Al3+

Li+ Ca2+

Na+ Sr2+

K+ Ba2+

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Learning Check

A. Number of valence electrons in aluminum1) 1 e- 2) 2 e- 3) 3 e-

B. Change in electrons for octet1) lose 3e- 2) gain 3 e- 3) gain 5 e-

C. Ionic charge of aluminum 1) 3- 2) 5- 3) 3+

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Solution

A. Number of valence electrons in aluminum3) 3 e-

B. Change in electrons for octet1) lose 3e-

C. Ionic charge of aluminum 3) 3+

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Learning Check

Give the ionic charge for each of the following: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-

2) 3+ 2) 3- 3) 5-

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Solution

Give the ionic charge for each of the following:

A. 12 p+ and 10 e-

2) 2+

B. 50p+ and 46 e-

2) 4+

C. 15 p+ and 18e-

2) 3-

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Learning Check

A. Why does Ca form a Ca2+ ion?

B. Why does O form O2- ion?

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Solution

A. Why does Ca form a Ca2+ ion?

Loses 2 electrons to give octet

2-8-8-2 2-8-8 (like Ar)

B. Why does O form O2- ion?

Gains 2 electrons to give octet

2-6 + 2e- 2-8 (like Ne)

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Ions from Nonmetal Ions

In ionic compounds, nonmetals in 5A, 6A, and

7A gain electrons from metals

Nonmetal add electrons to achieve the octet

arrangement

Nonmetal ionic charge:

3-, 2-, or 1-

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Fluoride Ion

unpaired electron octet

1 -

: F + e : F :

2-7 2-8 (= Ne)

9 p+ 9 p+

9 e- 10 e- 0 1 -

ionic charge

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Learning CheckComplete the names of the following ions: 5A 6A 7A

N3 O2 F

nitride __________ fluoride

P3 S2 Cl

___________ __________ _________

Br

_________

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Solution

5A 6A 7A

N3 O2 F

nitride oxide fluoride

P3 S2 Cl

phosphide sulfide chloride

Br

bromide