Upcoming SlideShare
×

Thanks for flagging this SlideShare!

Oops! An error has occurred.

×
Saving this for later? Get the SlideShare app to save on your phone or tablet. Read anywhere, anytime – even offline.
Standard text messaging rates apply

# Electronegativity part two

3,277
views

Published on

1 Like
Statistics
Notes
• Full Name
Comment goes here.

Are you sure you want to Yes No
• Be the first to comment

Views
Total Views
3,277
On Slideshare
0
From Embeds
0
Number of Embeds
0
Actions
Shares
0
0
0
Likes
1
Embeds 0
No embeds

No notes for slide

### Transcript

• 1. Adding Up the Difference
How to determine if a bond is ionic, polar covalent, or covalent
• 2. Calculate The Difference
To determine how evenly (or unevenly) two atoms will share a pair of electrons, we’ll need to compare the electronegativity values of each atom.
If the atoms have the same electronegativity value, they’ll share the electrons evenly.
The greater the difference in electronegativity, the more unevenly the electrons are shared (the inequity is always in favor of the MORE electronegative atom)
We’ll always be looking at the absolute value of the difference.
• 3. The Rules
The difference in electronegativity is zero.
The difference in electronegativity is greater than zero.
The difference in electronegativity is greater than or equal to 1.9 AND one atom is a metal and the other is a non-metal.
Covalent
Polar Covalent
Ionic
• 4. First Things First
This slideshow comes with a warning: we’ll use a cutoff value of 1.9 for deciding between ionic and polar covalent bonds. You should know, though, what cutoff your textbook/teacher/instructor/professor/exam/etc. will be using. It might be the same as mine, it might not be. If you don’t know, find out. And if you don’t find out, don’t blame me if you get it wrong on the exam!
• 5. Example One: Sodium Chloride
Consider the compound sodium chloride. The electronegativity values for sodium and chlorine are shown below. To calculate the difference in electronegativity, we’ll consider the ABSOLUTE VALUE of the difference between the two values.
Sodium 0.9 Chlorine 3.0
Sodium chloride meets the two requirements for ionic bonding:
The difference in electronegativity is greater than 1.9
Sodium is a metal, and chlorine is a non-metal
Cl 3.0
-Na 0.9
2.1
• 6. Example Two: Chloroethane
The molecule chloroethane (C2H5Cl) has three types of bonds: Carbon-Carbon, Carbon-Hydrogen, and Carbon-Chlorine.
We’ll use the electronegativity values shown here to calculate the difference in electronegativity between the atoms in each bond.
Carbon: 2.5 Hydrogen: 2.1 Chlorine: 3.0
• 7. Example Two: Chloroethane
C 2.5
-C 2.5
0
C 2.5
-H 2.1
0.4
Cl 3.0
-C 2.5
0.5
{
Polar Covalent
Covalent
Note that Chloroethane contains both covalent and polar covalent bonds. This is not only “okay” – it’s normal!!!
• 8. Practice One
ElementEN
Fluorine 4.0
Oxygen 3.5
Chlorine 3.0
Nitrogen 3.0
Bromine 2.8
Carbon 2.5
Sulfur 2.5
Iodine 2.5
Hydrogen 2.1
Phosphorous 2.1
Magnesium 1.2
Lithium 1.0
Sodium 0.9
Label each of the following bonds as ionic, polar covalent or covalent. Use the electronegativity values on the right.
Na—F
K—Cl
C—O
N—H
C—S
Na—F is an ionic bond (4.0-0.9 = 3.1, and there is a metal and a non-metal)
K—Cl is an ionic bond (3.0-0.8 = 2.2, and there is a metal and a non-metal)
C—O is a polar covalent bond (3.5-2.5 = 1.0)
N—H is a polar covalent bond (3.0-2.5 = 0.5)
C—S is a covalent bond (2.5-2.5 =0)
• 10. Practice Two
ElementEN
Fluorine 4.0
Oxygen 3.5
Chlorine 3.0
Nitrogen 3.0
Bromine 2.8
Carbon 2.5
Sulfur 2.5
Iodine 2.5
Hydrogen 2.1
Phosphorous 2.1
Magnesium 1.2
Lithium 1.0
Sodium 0.9
Consider each of the following compounds. Identify EACH BOND as being ionic, polar covalent or covalent.
MgO
CO2
CH2O
NaBr