22.4 NotesCovalent Bonds

In the book Section 22.2

Objectives

Describe covalent bonds. Identify the particles produced by ionic

bonding and by covalent bonding. Distinguish between a nonpolar covalent

bond and an polar covalent bond.

Covalent Bonds

Occur when atoms share electrons Forms a molecule

Share because losing electrons takes too much energy

Single bonds = sharing of 2 electrons Typically two elements each donating

1 electron to share Water contains 2 single bonds

Each Hydrogen shares one electron with Oxygen sharing one electron

Covalent Bonds

A covalent bond can contain more than one pair of electrons

Example: Nitrogen (N2) Each nitrogen shares 3 electrons to form a

triple bondhttp://www.youtube.com/watch?v=yjge1WdCFPs

Unequal Sharing

Electrons are not always shared equally Strength of attraction is related to size,

charge and number of electrons One element has a stronger attraction Example: HCl

Chlorine atoms have stronger attraction than hydrogen

Polar Molecule

If charge is balanced but electrons are NOT shared equally

Has a slightly positive end and a slightly negative end

Nonpolar Molecule

Molecule in which electrons are shared EQUALLY

Does not have oppositely charged ends True of molecules made from two

identical atoms or molecules that are symmetric

http://www.elmhurst.edu/~chm/vchembook/153Acompare.html

Properties of Compounds

Ionic Compounds Covalent Compounds

Bond Type Electron transfer Electron sharing

Smallest Particle Ion Molecule

Electrical Conductivity Good Poor

State at Room Temp Solid Any

Forces Between Particles

Strong attraction between cations and anions

Strong bonds between atoms, weak attraction

between molecules

Oxidation Number

An oxidation number tells you how many electrons an atom has gained, lost, or shared to become stable For ionic compounds the oxidation number

is the same as the charge on the ion For example, a sodium ion has a charge of

1+ and an oxidation number of 1+.

+2+1

+3 -3 -2 -1

In-Class Assignment/Homework 22.2 Reinforcement WKT