1. Electronegativity

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

3. Most electronegative element!
Trend
Most electronegative element!

4. F > O > Cl,N > Br > C,S,I > H,P
Cause
She
Is a
Hungry
Person
Frank
Owes
Claire
Nine
Brownies
Put a comma in every third element
These elements separated by commas are equal in electronegativity
Memorize these!!!

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

7. e- poor e- rich F H d+ d- H F electron rich region electron poor
BONDS, NOT MOLECULE!!!

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

9. Partial charges, also known as dipoles, in the covalent molecules
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.)

10. Partial charges, also known as dipoles, in the covalent molecules
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.) d- d+ d- d- d- d+ d-

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

12. Practice
Which of the following bonds is polar covalent, which is non polar covalent, and which is ionic?
The bond in CsCl
The bond in H2S
The NN bond in H2NNH2
Ionic
Polar covalent
Non Polar covalent