1. Electronegativity

2. Ability of an atom to attract electrons towards itself in a chemical bond Electronegativity

3. Trend Most electronegative element!

5. Covalent Bond nonpolar equal sharing of electrons Electron density is symmetrical polar Unequal sharing of electrons Greater electron density near one element H—H

6. 6 H F F H electron rich region electron poor region e - riche - poor ++ --

7. 7 Covalent share e - Polar Covalent partial transfer of e - Ionic transfer e - Increasing difference in electronegativity Classification of bonds by difference in electronegativity DifferenceBond Type 0Covalent  2 Ionic 0 < and <2 Polar Covalent

8. The whole crossed arrow shows the shift in the electron density. It points towards the more electron rich region (more electronegative element.) The “plus” end shows the electron poor region (less electronegative element.) Partial charges, also known as dipoles, in the covalent molecules

9. -- -- ++ ++ -- -- -- The delta (greek letter) also shows the shift in the electron density. Delta – is the more electron rich region (more electronegative element.) The delta “plus” shows the electron poor region (less electronegative element.) Partial charges, also known as dipoles, in the covalent molecules

10. For each bond, indicate the shift in electron density.

11. Practice Which of the following bonds is polar covalent, which is non polar covalent, and which is ionic? a.The bond in CsCl b.The bond in H 2 S c.The NN bond in H 2 NNH 2 Ionic Polar covalent Non Polar covalent