Electronegativity

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

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

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

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

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

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

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

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

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

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

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

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

On Your Own Answers Place these from most to least electronegative Chlorine: 3.0 Bromine: 2.8 Iodine: 2.5 Lithium: 1.0 Sodium: 0.9

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.

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

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

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

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

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

Is what is Sodium Chloride? Sodium Chloride is ionic!

Another Example MgO

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

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

Your Turn! Hydrogen gas (H2): Hydrogen Bromide (HBr): 2.1-2.1=0 non-polar covalent Hydrogen Bromide (HBr): 2.8-2.1=0.7 polar covalent Formaldehyde (CH2O): C-H bond: 2.5-2.1= 0.4 non-polar covalent C-O bond 3.5-2.5= 1.0 polar covalent SnCl4 Tin Chloride 3.0-1.8=1.2 polar covalent CBr4 Carbon Tertabromide 2.8-2.5= 0.3 non-polar covalent

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

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

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

And Now an Exception (Just for Fun) Hydrogen Fluoride Hydrogen = 2.1 Fluoride = 4.0 4.0-2.1=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!!!!

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

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

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

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

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

Another Example O - H

Calculations Oxygen = 3.5 Hydrogen = 2.1

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

Calculations Oxygen = 3.5 Hydrogen = 2.1 3.5-2.1 = 1.4 Polar covalent

Depiction O H δ - δ +

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

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 2.1-3.5 Oxygen C-S 2.5-2.5=0 Neither!

Your Turn N H C Br P O C S