1. 22.4 Notes Covalent Bonds In the book Section 22.2

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.

3. 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

4. Covalent Bonds  A covalent bond can contain more than one pair of electrons  Example: Nitrogen (N 2 ) Each nitrogen shares 3 electrons to form a triple bond http://www.youtube.com/watch?v=yjge1WdCFPs

5. 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

6. Polar Molecule  If charge is balanced but electrons are NOT shared equally  Has a slightly positive end and a slightly negative end

7. 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

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

9. Properties of Compounds Ionic CompoundsCovalent Compounds Bond TypeElectron transferElectron sharing Smallest ParticleIonMolecule Electrical ConductivityGoodPoor State at Room TempSolidAny Forces Between Particles Strong attraction between cations and anions Strong bonds between atoms, weak attraction between molecules

10. 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+.

11. +2 +1 +3 -3-2

12. In-Class Assignment/Homework  22.2 Reinforcement WKT