Covalent Bonding

Table of ContentsLecture/Lab/Activity Date Pg#

22. The Periodic Table 9/24/10 4723. Periodic Def & Trends 9/27/10 4924. Electron config practice 10/4/10 5125. Ions and Oxidation Numbers 10/5/10 5326. Lewis Dot Diagram 10/6/10 5427. Intro to Chemical Bonding 10/7/10 5728. Covalent Bonding 10/12/10 61

Objective:The student will practice illustrating Lewis dot diagrams of covalent compounds after recording lecture notes

Agenda:Covalent Bonding– Lecture

Valence electrons- The e- involved in chemical bonding-These e- are in the outermost “n” level- Represented by the Lewis-electron dot structure

Ex. Sulfur

[Ne]3s23p4

Electron configuration S6 valence e-

Lewis-e- dot structure

Bond Formation

Write the Lewis-e- dot structure for Nitrogen!

[He]2s22p3

Electron configuration

5valence e-

N N N N5th e- placement is arbitrary

Practice Problem

Atoms will gain, lose, or share e- until they have 8 valence e- (octet rule).

There are exceptions!Ex. He only has 2 valence e-.

Covalent bonding: Bonding in which electrons are shared instead of transferred. Occurs between non-metals

Low melting & boiling point

Covalent Bonds

Determining the # of Bonds

1. Total Needed• 8 per atom• H & He = 2

2. Total Available• Count valence electrons

3. Needed – Available = # shared

In covalent compounds, atoms share e- to achieve octets for the valence e-.

F + FF

Bonding PairEach bonding pair represents a single covalent bond.

FF = F2

Diatomic MoleculeCovalent molecule made up of 2 atoms of the same element

F

Ex. F2 formation?

Starting Valence e- = 14

Final Valence e- = 14

HH

HH

Write the Lewis-e- dot structure for CH4.

CH

C +

HH

HH C

or

H

HH

Write the Lewis-e- dot structure for PCl3.

Cl+P PCl

ClCl

PClCl

Cl

or

Cl

Cl

What about ions like ClO2-……how do

we draw the Lewis-e- dot structure???

+ O +Extra e- from the negative superscript

O OCl

or

O OCl

Cl O

Multiple BondsCovalent compounds can share more

than one pair of valence e-.

Ex. CO2

+ CO O

2 shared e- pairs = double bond

CO O

or

C OO

Example N2

N N+ NN

or

3 shared e- pairs = triple bond

NN

Write the Lewis-e- dot structure for NO2

-.

O ON + O+ ON

NO O

or

Using the concept of electronegativity, we observe that there are two types of covalent bonds.

Polar Covalent: unequal sharing of electrons by atoms that creates a small dipole.Nonpolar Covalent: equal sharing of electrons, no dipole created.

Types of Covalent Bonds