Apoyos U.III Enlaces

2

Valence electrons are the outer shell electrons of an atom. The valence electrons are the electrons that participate in chemical bonding.

1 1 ns1

2 2 ns2

13 3 ns2np1

14 4 ns2np2

15 5 ns2np3

16 6 ns2np4

17 7 ns2np5

Group # of valence e- e- configuration

3

Lewis Dot Symbols for the Representative Elements & Noble Gases

4

Li + F Li+ F -

Enlace ionico

1s22s1 1s22s22p5 1s2 1s22s22p6

[He] [Ne]

Li Li+ + e-

e- + F F -

F - Li+ + Li+ F -

LiF

FORMA CORRECTA DE REPRESENTAR ESTRUCTURA DE LEWIS DE UN COMPUESTO CON ENLACE IONICO.

Thus, the simplest neutralizing ratio of Al3+ to O2− is 2:3; two

Al3+ ions have a total charge of +6, and three O2− ions have a

total charge of −6. So the empirical formula of aluminum oxide

is Al2O3, and the reaction is

Check Make sure that the number of valence electrons (24) is

the same on both sides of the equation. Are the subscripts in

Al2O3 reduced to the smallest possible whole numbers?

OTRO EJEMPLO DE ESTRUCTURA DE LEWIS DE COMPUESTOS CON ENLACE IONICO.

6

A covalent bond is a chemical bond in which two or more electrons are shared by two atoms.

Why should two atoms share electrons?

F F +

7e- 7e-

F F

8e- 8e-

F F

F F

Lewis structure of F2

lone pairs lone pairs

lone pairs lone pairs

single covalent bond

single covalent bond

LOS ELECTRONES SE COMPARTEN .

EJEMPLO DE ESTRUCTURA DE LEWIS DE COMPUESTOS CON ENLACE COVALENTE.

7

8e-

H H O + + O H H O H H or

2e- 2e-

Double bond – two atoms share two pairs of electrons

single covalent bonds

O C O or O C O

8e- 8e- 8e- double bonds

Triple bond – two atoms share three pairs of electrons

N N

8e- 8e-

N N

triple bond

or

EJEMPLO DE ESTRUCTURA DE LEWIS DE COMPUESTOS CON ENLACE COVALENTE.

RESONANCIA : Diferentes formas representar la estrucura de Lewis en una molecula, sin alterar sus propiedades físicas y químicas. Distribucion de enlaces y eletrones de maneras diferentes.

O O O + -

O O O + -

OJO; SEÑALAR QUE SON CARGAS PARCIALES CON EL SIMBOLO DELTA ( )

9

Algunas Excepciones de la regla del octeto.

SF6

S

F

F

F

F F

F

PF5

B

F F

F BF3

Be F F

BeF2

10

Lengths of Covalent Bonds

Bond Lengths

Triple bond < Double Bond < Single Bond

11

Electronegativity is the ability of an atom to attract toward itself the electrons in a chemical bond.

Electron Affinity - measurable, Cl is highest

Electronegativity - relative, F is highest

X (g) + e- X-(g)

12

The Electronegativities of Common Elements

13

AB2 2 0 linear linear

Class

# of atoms bonded to

central atom

# lone pairs on

central atom Arrangement of electron pairs

Molecular Geometry

VSEPR

AB3 3 0 trigonal planar trigonal planar

AB4 4 0 tetrahedral tetrahedral

14

15

bonding-pair vs. bonding- pair repulsion

lone-pair vs. lone-pair repulsion

lone-pair vs. bonding- pair repulsion

> >

16

Formation of sp2 Hybrid Orbitals

17

Formation of sp3 Hybrid Orbitals

18

Formation of Covalent Bonds in CH4

19

# of Lone Pairs +

# of Bonded Atoms Hybridization Examples

2

3

4

5

6

sp

sp2

sp3

sp3d

sp3d2

BeCl2

BF3

CH4, NH3, H2O

PCl5

SF6

How do I predict the hybridization of the central atom?

1. Draw the Lewis structure of the molecule.

2. Count the number of lone pairs AND the number of atoms bonded to the central atom

20

21

22

Two Possible Interactions Between Two Equivalent p Orbitals