1. Electronegativity

2. What is electronegativity?
The ability of an element to attract bonding electrons to itself
What does that mean?

3. What is electronegativity?
The ability of an element to attract bonding electrons to itself
What does that mean?
Where do electrons spend more of their time
Where is a reaction more likely to occur

4. Remember from Physics! Opposite charges attract
Positive goes toward negative
Negative goes toward positive

6. Electronegativity
Place the following elements from most electronegative to least (these are the CHONPS elements):
Carbon
Hydrogen
Oxygen
Nitrogen
Phosphorous
Sulfur

7. Electronegativity Carbon (C): 2.5 Hydrogen (H) : 2.1 Oxygen (O): 3.5
Nitrogen (N): 3.0
Phosphorous (P): 2.1
Sulfur (S): 2.5

8. Electronegativity Hydrogen = Phosphorous: 2.1 Carbon=Sulfur: 2.5
Nitrogen: 3.0
Oxygen: 3.5

9. On Your Own Place these from most to least electronegative Lithium
Sodium
Chlorine
Bromine
Iodine

10. On Your Own Place these from most to least electronegative
Lithium (Li)
Sodium
Chlorine
Bromine
Iodine

11. On Your Own Place these from most to least electronegative
Lithium (Li)
Sodium (Na)
Chlorine
Bromine
Iodine

12. On Your Own Place these from most to least electronegative
Lithium (Li)
Sodium (Na)
Chlorine (Cl)
Bromine
Iodine

13. On Your Own Place these from most to least electronegative
Lithium (Li)
Sodium (Na)
Chlorine (Cl)
Bromine (Br)
Iodine

14. On Your Own Place these from most to least electronegative
Lithium (Li)
Sodium (Na)
Chlorine (Cl)
Bromine (Br)
Iodine (I)

15. On Your Own Answers Place these from most to least electronegative
Chlorine: 3.0
Bromine: 2.8
Iodine:
Lithium: 1.0
Sodium: 0.9

16. Why do we Need This?
To determine Bond type of a molecule (non-polar covalent, polar covalent, or ionic)
To determine whether a reaction will occur and where on a molecule it will occur.

17. How do we determine Polarity?
Basic arithmetic
Examples:
Sodium Chloride

18. How do we determine Polarity?
Basic arithmetic
Examples:
Sodium Chloride
Sodium = 0.9

19. How do we determine Polarity?
Basic arithmetic
Examples:
Sodium Chloride
Sodium = 0.9
Chloride = 3.0

20. How do we determine Polarity?
Basic arithmetic
Examples:
Sodium Chloride
Sodium = 0.9
Chloride = 3.0
Sodium Chloride: =2.1

21. What does this tell me?
If the number is between 0 and 0.5 the bond is non-polar covalent
If the number is between 0.5 and 1.8, the bond is polar covalent
If the number is larger than 1.8, the bond is ionic

22. Is what is Sodium Chloride?
Sodium Chloride is ionic!

23. Another Example
MgO

24. Another Example MgO (Magnesium Oxide) Mg=1.2 O = 3.5 3.5-1.2=2.3
Therefore, another ionic molecule!

25. Your Turn! Hydrogen gas (H2) Hydrogen Bromide (HBr)
Formaldehyde (CH2O)
SnCl4 (Give me the name as well)
CI4 (Give me the name as well)

26. Your Turn! Hydrogen gas (H2): Hydrogen Bromide (HBr):
=0 non-polar covalent
Hydrogen Bromide (HBr):
= polar covalent
Formaldehyde (CH2O):
C-H bond: = non-polar covalent
C-O bond = polar covalent
SnCl4 Tin Chloride
= polar covalent
CBr Carbon Tertabromide
= non-polar covalent

27. And Now an Exception (Just for Fun)
Hydrogen Fluoride
Hydrogen = 2.1
Fluoride = 4.0
=1.9

28. And Now an Exception (Just for Fun)
Hydrogen Fluoride
Hydrogen = 2.1
Fluoride = 4.0
=1.9
So it’s ionic by the calculations

29. And Now an Exception (Just for Fun)
Hydrogen Fluoride
Hydrogen = 2.1
Fluoride = 4.0
=1.9
So it’s ionic by the calculations
But it’s covalent by the rules you previously learned

30. And Now an Exception (Just for Fun)
Hydrogen Fluoride
Hydrogen = 2.1
Fluoride = 4.0
=1.9
So it’s ionic by the calculations
But it’s covalent by the rules you previously learned
Rule #1 of Drug Chemistry: Fluorine is weird!!!!

31. Where will electrons Spend more Time?
Carbon? Or Chlorine?

32. Where will electrons Spend more Time?
Carbon = 2.5 Or Chlorine = 3.0

33. Where will electrons Spend more Time?
Carbon = 2.5 Or Chlorine = 3.0 Rule: The larger the number, the more electronegative. The more electronegative, the more time electrons spend around that element

34. Where will electrons Spend more Time?
Carbon = 2.5 Or Chlorine = 3.0 Therefore, Chlorine!!!!

35. Arrow ALWAYS goes from + to -
How do we Show This?
C Cl
δ δ-
Arrow ALWAYS goes from + to -

36. Another Example
O - H

37. Calculations
Oxygen = 3.5
Hydrogen = 2.1

38. Therefore, Oxygen is more electronegative
Calculations
Oxygen = 3.5
Hydrogen = 2.1
Therefore, Oxygen is more electronegative

39. Calculations
Oxygen = 3.5
Hydrogen = 2.1
= 1.4
Polar covalent

40. Depiction
O H
δ δ +

41. Your Turn
N-H
C-Br
P-O
C-S

42. Your Turn N-H C-Br P-O C-S 3.0-2.1 = 0.9 Nitrogen 2.5-2.8 = 0.3
Bromine
P-O
Oxygen
C-S =0
Neither!

43. Your Turn
N H
C Br
P O
C S