1. Differences between Covalent Bonding and Ionic Bonding

2. Why this works
Electronegativity- ability of an atom to attract and hold bonding electrons.
Elements with a large difference in electronegativity will form an ionic bond, elements with a small difference will form covalent bonds.

3. Electronegativity Chart

4. What about the middle ground?
What if the difference in electronegativity isn’t large or small but in the middle?
For example H (2.1) and O (3.5)
These elements form a polar covalent bond.
Polar Covalent Bond- unequal sharing of electrons in the bond
the electrons stay around oxygen more than hydrogen

5. Polar covalent 4 electrons occupy this cloud.
Notice how much larger the cloud is around oxygen as compared to hydrogen.

6. Do any bonds have an equal sharing?
Yes, (normally the same element) when elements are equally electronegative like O2
In fact, anything with a very slim difference (less than 0.5) in electronegativity will pretty much equally share electrons.
Nonpolar covalent bonding- equal sharing of electrons in a bond

7. Bonds electron density

8. Why it is called polar
polar implies different ends have different charges
similar to a magnet.
Water has 2 polar covalent bonds, meaning
the electrons stay around oxygen more than H H
Oxygen
and this side
positive
That makes this
side negative H

9. Denoting positive and negative
Neither side is completely positive or negative,
they are only partially positive and partially negative.
 +
 + H H
Oxygen
The symbol  (lower case
delta) means partial
 2-

10. Effects of shape on polarity
Water is polar because it is bent
CO2 is nonpolar because it is
linear - O O C O - H H + +
To be polar you
need a positive end
and a negative end
Center of positive and negative charge is in
The same place.

11. Conservation of…
Mass
Mass is neither created nor destroyed in a reaction.
The mass of the reactants is equal to the mass of the products.
This is often forgotten, or is a common misconception due to certain reactions.

12. Reactions in a water solution
What happens when ions dissolve in water?
Ions become free floating.
In a solid, they are “stuck together”.
In a solution, they are free to move.

13. Conduction of Electricity
Pure water does NOT conduct electricity
~there are no (+) and (-) particles to move the elctrons
For water to conduct electricity you must dissolve an electrolyte in it.
Electrolyte- any substance that increases a solvent’s conductivity

14. Precipitation Reaction
~ a reaction where a solid product is produced from dissolved reactants
Precipitate- solid falling out of solution
It will appear to make the solution cloudy

15. homework
Read section 6.6 and 6.7 Pg
Prob 23-30; 78-81