Bonding : Bonds and Electronegativity

Types of Bonds

- There are three types of bonds :

• Ionic (metal - non metal) - e- and transferred from metal to non metal
• Covalent (non metal - non metal) e- shared between non metals
• Metallic (metal) - Holds pure metal together by electrostatic attraction

Electronegativity

- Electronegativity (en) is a measure of an atom's attraction for electrons in a bond

- Fluorine = 4.0

- Chlorine = 3.0

- Cesium = 0.9

- Atoms with greater en attract e- more

- Polar covalent bonds form from an unequal sharing of e-

- Non-polar covalent bonds form from equal sharing

Bonds (no.. Not James Bond)

- The type of bond formed can be predicted by looking at the difference in electronegativity of the element

en > 1.7 = Ionic bond

en < 1.7 = Polar covalent bond

en = 0 is non-polar covalent bond

Examples

- Predict the type of bond formed

O - O

Since the en charge of Oxygen is 3.44, we would sub it in like math.

3.44 - 3.44 = 0

Since it equals zero, you have to look back at the Bonds, and since it equals 0, it's a non-polar covalent bond

- Identify the positive and negative side of the Polar Bonds

Now you would have to figure out the positive the negative of each chemical in the electronegativity.

You need to know a symbol that means partially. ( It's suppose to look like a really messed up six, you're pretty much drawing it backwards, but for now we'll use this, '[')

Example

N - O
3.04 - 3.44 = 0.40 - Polar covalent

You would think that would be the answer, but it's not.
You would need to state which is positive and which is negative.
So you're final answer would be :

[+N - O[-
That means, Nitrogen is partially positive and Oxygen is partially negative.
And don't worry about if the number you subtract becomes a negative number. You would always want to imply the Absolute value. (Example)

|N - O = ?|

|3.04 - 3.44 = ?|
= |-0.40|
=0.40

Here's a video example of what I was trying to explain.

http://www.youtube.com/watch?v=Kj3o0XvhVqQ

-Meldrick Mendoza