1. Forming single, double, and triple bonds
Covalent Bonds
Forming single, double, and triple bonds

2. Covalent Bonding
Remember, when atoms bond covalently, there is a sharing of electrons between the two atoms.
However, not all of the electrons are involved in the bond, so there are two different types of electron pairs.
Bonding Pair: Shared (shown by lines)
Lone Pairs: Unshared (shown by pairs of dots)

3. There are also a few types of covalent bonds and the type of covalent bond depends on how many pairs of electrons are shared.

4. Single Covalent Bonds Double Covalent Bonds Triple Covalent Bonds 1 2
The sharing of ______ pair of electrons
Double Covalent Bonds 2
The sharing of ______ pair of electrons
Triple Covalent Bonds 3
The sharing of ______ pair of electrons

5. Strength of Bonds
bond
Distance separating nuclei - _________ ___________
Depends on the size of the atoms - _________ ___________
Pairs shared – more electrons shared, _________ ___________
(_____________ has smallest bond length)
Smaller bond length - _________ ___________
length
atomic
radii
closer
together
Triple bond
stronger
bond

6. Strength of Bonds
Bond dissociation energy – energy to _________ ___________
Energy must be _________ to break bonds
Direct relationship between bond energy and bond length - _________ bond length, _________ bond, _________ bond energy
break
bonds
added
smaller
stronger
more

7. So, how do scientists decide how many electrons are shared
So, how do scientists decide how many electrons are shared? One way is by drawing Structural Formulas a.k.a. Lewis Formulas

8. NASL Method: Let’s look at H3P
Create a skeleton of the chemical formula
_____________element in center first
_____________electronegative in center if there is a choice
­_____________ is never in the middle
Single
Least
Hydrogen P H

9. N P H H H Needed 8 Hydrogen 2 Determine number of electrons __________
Atoms want ____ electrons.
__________only wants ___ electrons. 8
Hydrogen 2 P H H H

10. A P H Available Add total number of _________ electrons. valence
Determine number of electrons __________
Add total number of _________ electrons.
valence H P

11. S = ____- ____ H P N A Shared Divide by ____ to get number of bonds 2
Determine ___________ electrons.
Divide by ____ to get number of bonds
Remember a line represents ____ electrons.
___________ can only make a ___________ ___________. 2 2
Hydrogen
single
bond P H

12. S = ____- ____ H H P H N A Shared
Determine ___________ electrons.
Divide by ____ to get number of bonds
Remember a line represents ____ electrons.
___________ can only make a ___________ ___________. 2 2
Hydrogen
single
bond H H P H

13. L = ____- ____ H P A S Lone-pair
Determine ___________ electrons.
If any electrons are left, place pairs of electrons on the _______________ atom(s) until they are “______________”.
Next, if any electrons are left, place them on the ___________ atom.
outside
Happy
center P H

14.  H    H P H Happy Hydrogen :___________ 2 electrons
Check to make sure all atoms are “happy”.
Happy Hydrogen :___________
Happy everything else:__________
2 electrons
8 electrons  H    H P H

15. Let’s try some examples
H2O
CF4

16. NCl2Br
CO2

17. Polyatomic Ions
Take charge into consideration. (Add negative to total, subtract positive from total of electrons.)
Put brackets around structure with charge on outside right corner

18. Let’s look at CO32- and NH4+1