LecturePLUS Timberlake 1

Chemical Bonds

Attraction between two or more atomsInteraction between valence electronsIonic bondsCovalent bonds

LecturePLUS Timberlake 2

Valence Electrons

Electrons in the highest (outer) electron level

Have most contact with other atoms

Known as valence electrons

Outer shelI of noble gases the outer shell

contains 8 valence electrons as s2p6 (except

He = 2)

Example: Ne 1s2 2s2 2p6

Ar 1s2 2s2 2p6 3s2 3p6

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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 B1

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 B1

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 +

1s22s22p63s1 1s22s22p6 ( = Ne)

11 p+ 11 p+

11 e- 10 e-

0 1+

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Formation of Magnesium Ions

Magnesium atom Magnesium ion

Mg – 2e Mg2+

1s22s22p63s2 1s22s22p6 (Ne)

12 p+ 12 p+

12 e- 10 e-

0 2+

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Cations of Some Representative Elements

Group 1A Group 2A Group 3AH+ Mg2+ Al3+

Li+ Ca2+

Na+ Sr2+

K+ Ba2+

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Learning Check B 2

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 B 2

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 B 3

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 B 3

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 B 4

A. Why does Ca form a Ca2+ ion?

B. Why does O form O2- ion?

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Solution B 4

A. Why does Ca form a Ca2+ ion?

Loses 2 electrons to give octet

1s2 2s2 2p6 3s2 3p6 4s2

1s2 2s2 2p6 3s2 3p6 (like Ar)

B. Why does O form O2- ion?

Gains 2 electrons to give octet

1s2 2s2 2p4 + 2e-

1s2 2s2 2p6 2-8 (like Ne)

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Transition Metals

• Lose s electrons from the highest occupied

energy level.

• May also lose one or more d electrons.

• Most form 2 or more positive ions

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Fe2+ and Fe3+

Fe atom: 1s2 2s2 2p6 3s2 3p6 4s2 3d6

Loss of 4s2 electrons (outermost shell)

Fe2+ ion: 1s2 2s2 2p6 3s2 3p6 4s0 3d6

Loss of 3d1 electron

Fe3+ ion: 1s2 2s2 2p6 3s2 3p6 4s0 3d5

A 3d5 (half-filled) subshell is stable

LecturePLUS Timberlake 19

Some Transition Metal Ions

1+ 2+ 1+ or 2+ 2+ or 3+

Ag+ Cd2+ Cu+, Cu2+ Fe2+, Fe3+

silver cadmium copper(I) ion iron(II) ion

ion ion copper (II) ion iron(III) ion

Zn2+

zinc ion

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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 Ions

unpaired electron octet

1 -

: F + e : F :

1s22s22p5 1s22s22p6 = Ne

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Some Nonmetal Ions 5A 6A 7A

N3 O2 F

nitride __________ fluoride

P3 S2 Cl

___________ __________ _________

Br

_________

I

iodide ion

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Some Nonmetal Ions

5A 6A 7A

N3 O2 F

nitride oxide fluoride

P3 S2 Cl

phosphide sulfide chloride

Br

bromide

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Ionic Compounds

Attraction between + ions and - ions

Electrons go from metals to nonmetals

electron transfer

metal nonmetal ion+ ion-–

Electrons lost = Electrons gain

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Formulas of Ionic Compounds

Formulas of ionic compounds are determined from the charges on the ions

atoms ions

–

Na + F : Na+ : F : NaF

sodium fluorine sodium fluoride formula

Charge balance: 1+ 1- = 0

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Writing a Formula

Write the formula for the ionic compound that will form between Ba2+ and Cl.

Solution:

1. Balance charge with + and – ions

2. Write the positive ion of metal first, and the

negative ion Ba2+ Cl

Cl3. Write the number of ions needed as

subscripts BaCl2

LecturePLUS Timberlake 27

Learning Check B 5

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 is

1) Al3Cl 2) AlCl2 3) AlCl3

C. The formula of Fe3+ and O2- is

1) Fe3O2 2) FeO3 3) Fe2O3

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Solution B 5

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