1. Warm Up #20 Define electronegativity.
Which element is the most electronegative?
Why is this element the most E.N.?
Put these elements in order from least to most E.N. I, Cl, Br, S, H, P, O, F, N,C,
** hint- “brownies”
Ability of an atom to attract electrons towards itself in a chemical bond
Nitrogen
Nitrogen has the most number of protons to attract another element’s valence e- with the fewest electrons of its own shielding those protons
F > O > Cl,N > Br > C,S,I > H,P

2. Electronegativity

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

4. Most electronegative element!
Trend
Most electronegative element!

5. 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!!!

7. Covalent Bond nonpolar polar H—H H—F equal sharing of electrons
Electron density is symmetrical
Unequal sharing of electrons
Greater electron density near one element
H—H
electron poor
region
electron rich
region
H—F

8. e- poor
e- rich
BONDS, NOT MOLECULE!!! F H d+ d-

11. Polyatomic molecules
Nonpolar
Polar

12. Bond moments and resultant dipole moments in NH3 and NF3.

13. 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.)

14. Partial charges, also known as dipoles, in the covalent molecules
The delta (greek letter) also shows the shift in the electron density. Delta “negative” 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-

15. For each bond, indicate the shift (or pull) in the electron density.

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

17. F > O > Cl, N > Br > C, S, I > H, P
Trend
Most electronegative element!

18. Practice
In each pair of bonds, put a (*) next to the more polar bond using your worksheet numbers and use an arrow (+) to show the direction of the polarity in each bond.
H—S and B—C
N—N and N—H   *
=0.4, =0.5  *
=0, =0.9