1. Introduction to Bonding and electron dot/lewis structures
Chemistry

2. Why is bonding important??
Without bonding the universe would be a mass of individual atoms.
The type of bond defines the properties of a substance.
NaCl…shape
H2O and oil…dissolving
                                             

3. Electronegativity
Ability of atoms within a molecule to attract electrons

4. Polar
Describes a bond with an unequal distribution of electrons

5. Nonpolar
Describes a bond with an equal distribution of electrons

6. Covalent
Describes a bond where electrons are shared

7. Ionic
Describes a bond where electrons are transferred

8. DETERMINING BOND TYPE Calculate the difference in electronegativities:
> 1.7 = ionic (electrons transfer)
= polar covalent (electrons
are shared unequally)
<0.5 = nonpolar covalent (equal sharing of electrons)

9. EXAMPLE: 1. H2
a) Calculate the difference in electronegativities: 2.2 – 2.2 = 0  nonpolar covalent (equal sharing) b) Draw the electron dot/Lewis structure: H + H = H H [recall the “duet rule”—H wants 2 e-]

10. Nonpolar Covalent Bonds
Describes a bond where electrons are shared equally
Less than 0.5 electronegativity difference.
Let’s look at an animation of this with H2: H2
EN=0 ( (

11. NON-POLAR COVALENT BONDS
Covalent Bonds: Dogs of equal strength share equally. Covalent bonds can be thought of as two or more dogs with equal attraction to the bones. 
They share equally.

12. NON-POLAR COVALENT BONDS
Since the dogs are identical, then the dogs share the bones evenly.  Since one dog does not have more of the bone than the other dog, the bone is equally shared between both dogs. One dog does not have more than the other.

13. EXAMPLE: 2. H2O
a) calculate the difference in electronegativities: 3.5 – 2.2 = 1.3  polar covalent (unequal sharing) b) Draw the electron dot/Lewis structure: H + H + O = H O H [recall the “duet rule”—H wants 2 e-]

14. Polar Covalent Bonds
Describes a bond where electrons are shared unequally
Electronegativity (EN) difference is between 0.5 and 1.7.
Let’s look at an animation of this with H2O and HBr:
H2O
END=1.4
HBr
END=0.7 ( (

15. POLAR COVALENT BONDS
Unevenly matched dogs that are willing to share. These bonds can be thought of as two or more dogs that have different desire for bones. They share unequally.

16. POLAR COVALENT BONDS
The bigger dog has more strength to possess a larger portion of the bones.  Sharing still takes place but is an uneven sharing. 

17. EXAMPLE: 3. NaF
a) calculate the difference in electronegativities: 4.0 – 0.9 = 3.1  ionic (electrons are transferred) b) Draw the electron dot/Lewis structure: Na + F = Na F - +

18. Ionic Bonds Describes a bond where electrons are transferred.
Greater than 1.7 electronegativity difference.
Let’s look at an example of this with NaCl:
NaCl
EN=2.1 ( (

19. IONIC BONDS
One big greedy thief dog! Ionic bonding can be best imagined as one big greedy dog stealing the other dog's bone. 

20. The bone represents the electron that is up for grabs.
IONIC BONDS
The bone represents the electron that is up for grabs.
When the big dog gains an electron he becomes negatively charged, and the little dog who lost the electron becomes positively charged. 
These two ions (that's where the name ionic comes from) are attracted very strongly to each other as a result of the opposite charges.

21. Electron tug-of-war analogy
LOW Electronegativity
HIGH Electronegativity

22. equal sharing  covalent bond
It’s a tie… e-
equal sharing  covalent bond

23. The non-metal is pulling harder...
So what would unequal sharing be?
polar covalent

24. Transfer of electrons  ionic bond
The non-metal wins! e-
Transfer of electrons  ionic bond