METALLIC BONDbond found in

metals; holds metal atoms together

very strongly

Metallic Bond

• Formed between atoms of metallic elements• Electron cloud around atoms • Good conductors at all states, lustrous, very

high melting points• Examples; Na, Fe, Al, Au, Co

Ionic Bond, A Sea of Electrons

Metals Form Alloys

Metals do not combine with metals. They form Alloys which is a solution of a metal in a metal.Examples are steel, brass, bronze and pewter.

C. Johannesson

• NH4+

1 N × 5e- = 5e-

4 H × 1e- = 4e-

9e- HH N H

H

- 1e-

8e-

- 8e-

0e-

C. Polyatomic Ions

C. Johannesson

D. Resonance Structures

• Molecules that can’t be correctly represented by a single Lewis diagram.

• Actual structure is an average of all the possibilities.

• Show possible structures separated by a double-headed arrow.

C. Johannesson

D. Resonance Structures

OO S O

OO S O

OO S O

SO3

Exceptions to the Octet Rule

• Molecules containing atoms of Group 3A elements, particularly boron and aluminum

Aluminum chloride

:

:

:

F B

F

F

Cl Al

Cl

Cl

6 electrons in the valence shells of boron

and aluminum

Boron trifluoride

: :

: :

: :

::

::

:

::

::

Exceptions to the Octet Rule

• Atoms of third-period elements have 3d orbitals and may expand their valence shells to contain more than 8 electrons– phosphorus may have up to 10

::

Phosphorus pentachloride

Phosphoricacid

P

ClCl Cl

Cl ClCH3-P-CH3

CH3Trimethyl-phosphine

H-O-P-O-HO

O-H

:

:

::

:

::

::

:: :

:

::

:

::

:

:

:

Exceptions to the Octet Rule

– sulfur, another third-period element, forms compounds in which its valence shell contains 8, 10, or 12 electrons

:

::H-S-H CH3-S-CH3 H-O-S-O-H

O

OO

Sulfuricacid

Hydrogensulfide

Dimethylsulfoxide

::

::

: : : :

: :

C. Johannesson

A. VSEPR Theory• Valence Shell Electron Pair Repulsion

Theory

• Electron pairs orient themselves in order to minimize repulsive forces.

C. Johannesson

A. VSEPR Theory• Types of e- Pairs

– Bonding pairs - form bonds– Lone pairs - nonbonding e-

Lone pairs repel more strongly than

bonding pairs!!!

C. Johannesson

A. VSEPR Theory• Lone pairs reduce the bond angle between

atoms.

Bond Angle

C. Johannesson

• Draw the Lewis Diagram.• Tally up e- pairs on central atom.

– double/triple bonds = ONE pair

• Shape is determined by the # of bonding pairs and lone pairs.

Know the 8 common shapes & their bond angles!

B. Determining Molecular Shape

C. Johannesson

C. Common Molecular Shapes

2 total2 bond0 lone

LINEAR180°BeH2

C. Johannesson

3 total3 bond0 lone

TRIGONAL PLANAR120°

BF3

C. Common Molecular Shapes

C. Johannesson

C. Common Molecular Shapes

3 total2 bond1 lone

BENT<120°

SO2

C. Johannesson

4 total4 bond0 lone

TETRAHEDRAL109.5°

CH4

C. Common Molecular Shapes

C. Johannesson

4 total3 bond1 lone

TRIGONAL PYRAMIDAL107°

NH3

C. Common Molecular Shapes

C. Johannesson

4 total2 bond2 lone

BENT104.5°

H2O

C. Common Molecular Shapes

C. Johannesson

5 total5 bond0 lone

TRIGONAL BIPYRAMIDAL

120°/90°

PCl5

C. Common Molecular Shapes

C. Johannesson

6 total6 bond0 lone

OCTAHEDRAL90°

SF6

C. Common Molecular Shapes

C. Johannesson

• PF3

4 total3 bond1 lone

TRIGONAL PYRAMIDAL

107°

D. Examples

C. Johannesson

• CO2

2 total2 bond0 lone LINEAR

180°

D. Examples