1. Covalent Bonding & Resonance Structures 4.2.1 4.2.3 4.2.4

2. What is a covalent bond anyway?  4.2.1 – Describe the covalent bond as the result of electron sharing. The electron pair is attracted by both nuclei leading to a bond which is directional in nature. Both single and multiple bonds should be considered.

3. Covalent Bond Length and Strength  The length and strength of a covalent bond is closely related to its bond order. There are two definitions of bond order and we are going to stick with the ultra simple one. Bond order is the number of bonds holding two atoms together.

4. Covalent Bond Length and Strength  The length and strength of a covalent bond is closely related to its bond order. Bond order is inversely related to bond length. ○ So a double bond will be ______________ than a single bond. ○ Shorter

5. Covalent Bond Length and Strength  The length and strength of a covalent bond is closely related to its bond order. Bond order is directly related to bond strength. ○ So a double bond will be ______________ than a single bond. ○ Stronger

6. Covalent Bond Length and Strength Bond# of e - Bond Order Bond Strength Bond Length Single21WeakestLongest Double42 Triple63StrongestShortest

7. Resonance Structures  Resonance occurs when more than one Lewis structure exists for a molecule The individual structures are called resonance structures and are written with a double headed arrow between them. The actual structure is not any of the 3 shown. It is NOT flipping back and forth but is rather an average, or intermediate, of the 3.

8. Homework  Resonance Structures Worksheet Try a couple tonight, entire worksheet (both sides) is due Monday.