1. Section 8.2 The Nature of Covalent Bonding

2. The Octet Rule Atoms share electrons so they have a filled valence shell. Atoms share electrons so they have a filled valence shell. Most want 8 electrons in the outer shell- like the noble gases. Most want 8 electrons in the outer shell- like the noble gases. Hydrogen and Helium are exceptions! Hydrogen and Helium are exceptions!

3. Who is likely to form covalent bonds? Non-metallic atoms in Groups 4A, 5A, 6A, and 7A Non-metallic atoms in Groups 4A, 5A, 6A, and 7A

4. Types of Covalent Bonds Single Single Double Double Triple Triple

5. Single Covalent Bonds Formed when a pair of electrons (two total electrons) are shared between atoms. Formed when a pair of electrons (two total electrons) are shared between atoms. Showed by two dots in an electron dot diagram Showed by two dots in an electron dot diagram Showed by a dash in a structural diagram Showed by a dash in a structural diagram

6. Unshared electron pairs Indicated by dots Indicated by dots Also called lone pairs or non-bonding pairs Also called lone pairs or non-bonding pairs

7. Double and Triple Covalent Bonds A double bond is formed when two electron pairs are shared between atoms. A double bond is formed when two electron pairs are shared between atoms. A triple bond is formed when three electron pairs are shared between atoms. A triple bond is formed when three electron pairs are shared between atoms.

8. Why do polyatomic ions have a charge? If the charge on a polyatomic ion is negative, there are extra electrons added to the valence electrons: If the charge on a polyatomic ion is negative, there are extra electrons added to the valence electrons:

9. Resonance A way to envision bonding in certain molecules. A way to envision bonding in certain molecules. A resonance structure: one that occurs when it is possible to draw two or more valid electron dot structures that have the same number of electron pairs for a molecule or ion. A resonance structure: one that occurs when it is possible to draw two or more valid electron dot structures that have the same number of electron pairs for a molecule or ion.

10. Ozone: Example of Resonance

11. VSEPR Theory Molecules are three dimensional Molecules are three dimensional VESPR Theory accounts for this VESPR Theory accounts for this Stands for: Stands for: Valence Shell Electron Pair Repulsion

12. VSEPR Continued This theory states that unshared electron pairs push away from each other so they stay as far away from each other as possible. This theory states that unshared electron pairs push away from each other so they stay as far away from each other as possible. The result: the bonds “bend” to form angles with the central atom and give molecules three-dimensional shapes The result: the bonds “bend” to form angles with the central atom and give molecules three-dimensional shapes

13. # atoms ShapeAngleExample 2Lineardiatomic 180º N2N2N2N2 3Lineartriatomic CO 2 3Benttriatomic 105º H2OH2OH2OH2O 4TrigonalPlanar 120 ⁰ AlCl 3 4Pyramidal 107º NH 3 5Tetrahedral 109.5º CH 4