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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