Fundamentals of Chemical Bonding: Electron Sharing and Ionics, Study notes of Chemistry

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Basic Concepts of Chemical Bonding

Cover 8.1 to 8.7 EXCEPT

Omit Energetics of Ionic Bond FormationOmit Born-Haber Cycle

Omit Dipole Moments

ELEMENTS & COMPOUNDS

• Why do elements react to form compounds ?• What are the forces that hold atoms together

in

molecules

and

ions

in ionic compounds?

CHEMICALCHEMICALCHEMICALCHEMICAL

BONDSBONDSBONDSBONDS

BONDSBONDSBONDSBONDS

attractive force holding atoms together

Single Bond

involves an electron

pair

e.g. H

2

Double Bond

involves two electron

pairs

e.g. O

2

Triple Bond

: involves three electron

pairs

e.g. N

2

TYPES OF CHEMICALTYPES OF CHEMICALTYPES OF CHEMICAL

BONDSBONDSBONDSBONDS

BONDSBONDSBONDSBONDS

Ionic Polar Covalent

Two Extremes

Covalent

The

POLAR COVALENTPOLAR COVALENTPOLAR COVALENTPOLAR COVALENT

bond

is In-between

• the

IONIC BOND

[

transfer

of electrons ]

and

• the

COVALENT BOND

[ shared electrons]

The pair of electrons in a polar covalent bond are

not shared equally

DISCRIPTION OF ELECTRONS

How Many Electrons?

2. Electron Configuration3. Orbital

Diagram

Quantum Numbers

.

LEWIS SYMBOLS

LEWIS SYMBOLS

The Octet Rule

Atoms

gain, lose, or share electrons

until they are surrounded by

8 valence electrons

s

2

p

6

All noble gases

[EXCEPT HE]

have

s

2

p

6

configuration.

Note:

There are exceptions to the octet rule.

II. Covalent Bonding

II. Covalent Bonding

results from the

sharing

of electrons

between the atoms.

For example

H

H

→

H

H

or

H

H

Each pair of shared electrons constitutes

one chemical bond.

Cl

Cl

Cl Cl

Bonding & Non Bonding Electrons

Bonding

Electrons: electrons between elements

How many Bonding electrons in

Hydrogen?

Chlorine?

NonBonding

Electrons: those not used in bonding

How many Non Bonding electrons in

Hydrogen?

Chlorine?

Covalent Bonding

Covalent Bonding

When two atoms of the

same kind

bond, neither of them wants to lose orgain an electron

Therefore, they must share electronsEach pair of shared electrons constitutes

one chemical bond.

Strengths of Covalent Bonds

Strengths of Covalent Bonds

We know that multiple bonds are shorterthan single bonds.

We know that multiple bonds are strongerthan single bonds.

As the number of bonds between atomsincreases, the atoms are held closer andmore tightly together.

H

δδδδ

+

F

δδδδ

-

There is more electron density on F than on H.Since there are two different “ends” of the

molecule, HF has a

di pole.

C- H

Bond

Lewis dot formula

C

for carbon

H

Lewis dot formula

H · ·

C

· · H

for methane

H