1. Ch. 16 Notes---Covalent Bonds
____________ electrons between two atoms in order to fill the outer energy level (or shell)
Each bond involves the sharing of _____ _________ of electrons.
Single Bonds= __ e-’s Double Bonds= __ e-’s Triple Bonds=__ e-’s
Sharing
one pair 2 4 6

2. Ways to Represent Covalent Bonds in Compounds
“Circled Arrows” for bonds.
a) H H ___ 1s
H ___
b) F F …___ ___ ___ ___
2s p
F …___ ___ ___ ___ ↑ ↑ ↑ ↓ ↑ ↓ ↑ ↓ ↑ ↑ ↓ ↑ ↓ ↑ ↓ ↑

3. c) NH3 N …___ ___ ___ ___ 2s 2p d) H2O O …___ ___ ___ ___↑ ↓ ↑ ↑ ↑
H ___ 1s ↑
H ___ 1s ↑
H ___ 1s ↑ ↑ ↓ ↑ ↓ ↑ ↑
H ___ 1s ↑
H ___ 1s ↑

4. Ways to Represent Covalent Bonds in Compounds
(2) “Dots” for bonds.
a) H H · · H 
b) F :F· ·F: 
c) N :N · ·N:  (triple bond)
d) NH3
H:H .. .. .. ..
:F:F: .. .. .. ..
:N::N: ..
H:N:H .. H

5. Ways to Represent Covalent Bonds in Compounds
(3) “Lines” for bonds.
a) H2
b) F2
c) N2
d) NH3
e) H2O
H–H .. ..
:F–F: .. ..
:N≡N:
H–N–H ׀ H ..
H–O: ׀ H

6. Coordinate Covalent Bonds
Both of the electrons that make the bond come from the ________ _______________ .
Example: CO (carbon monoxide)
same
element
C …___ ___ ___ ___
2s p ↑ ↓ ↑ ↑
O …___ ___ ___ ___
2s p ↑ ↓ ↑ ↓ ↑ ↑ ..
:C O: .. ..
Two of the bonds are “normal”, and the third bond is a coordinate covalent bond. –
:C O: – ←

7. Carbon’s Hybrid Orbital C …___ ___ ___ ___ (Before) 2s 2p↑ ↓ ↑ ↑
C …___ ___ ___ ___ (After: 4 covalent bonds available) ↑ ↓ ↑ ↑ ↑
2sp3
Practice Problem: Draw CH4 using arrows, dots, and lines for bonds.
C …___ ___ ___ ___ ↑ ↑ ↑ ↑
2sp3
H ___ 1s ↑
H ___ 1s ↑
H ___ 1s ↑
H ___ 1s ↑

8. “HONClBrIF” The 7 Diatomic Elements
Some elements will covalently bond to themselves to form a molecule composed of ____ atoms.
These elements are never found in nature as single atoms. Instead, they will be bonded as a ________ when they are in the “_________________” state.
The 7 diatomic elements are the gases H, O, N, and all of the _________________, (Group 7A).
H2, O2, N2, Cl2, Br2, I2, F2
“HONClBrIF”
two
pair
elemental
halogens

9. PCl5 (___ e-) SF6 (___ e-) BF3(___e-)
Octet Rule
Atoms want ___ e-’s in their outer shell when forming compounds.
This will mean ___ dots around them all together. This is the stable e- configuration of a __________ _______!
Important exception: Hydrogen = only needs __ to be full (like He).
Other Exceptions:
PCl5 (___ e-) SF6 (___ e-) BF3(___e-) 8 8
noble gas 2 10 12 6

10. Resonance
Resonance is the ability to draw 2 or more different e- dot notations that obey the octet rule.
Examples: O3 (ozone) and SO2
Practice Problem: Draw the resonance structures for CO3-2.

11. VSEPR Theory: Molecular Shapes
Most shapes are based on a __________________.
Examples: CH4 CCl4
Removing the top of the tetrahedral makes the ________________ shape.
Examples: NH PCl3
tetrahedral
pyramidal

12. VSEPR Theory: Molecular Shapes
Removing one side of the pyramid makes the _____________ shape.
Examples: H2O H2S
If there are only two atoms bonded, it is ______________.
Examples: O2 HCl CO2 (linear because of its double bonds.)
bent
linear

13. VSEPR Theory: Molecular Shapes
The last shape we will need to know is called “trigonal planar”. “Trigonal” means that the central atom is bonded to ___ other atoms. “Planar” means that the 3 atoms all lie in the same ______________.
Example: BF3
(Notice that Boron will only have ___ e-’s around it. The missing pair of electrons will make it planar instead of ________________.) 3
plane 6
pyramidal

14. Polar and Nonpolar Bonds
Even though the electrons in a covalent bond are shared, sometimes the attraction for the bonded pair, (the _____________________), is uneven. This gives rise to 3 bond types.
nonpolar covalent bonds: ____________ sharing of the e- pair
polar covalent bonds: ________________ sharing of the e- pair
ionic bonds: a ___________ of e-’s from the metal to the nonmetal
This last type of bond will be discussed in detail in Chapter 15.
How To Determine the Bond Type
Bond type is based on the electronegativity _____________ between the two bonded atoms.
(See p.405 for electronegativity values.)
electronegativity
equal
unequal
transfer
difference

15. How To Determine the Bond Type
0 to 0.4 = ______________ covalent bond
0.5 to 1.7 = _____________ covalent bond
Above 1.7 = _______________ bond
Practice Problems: Determine the type of bond that forms between the atoms in the following compounds.
a) CO2 b) NaCl c) CH4
nonpolar
polar
ionic
1.0 = polar covalent
2.1 = ionic
0.4 = nonpolar covalent

16. Polarity of Molecules
One side is slightly (__) and the other side is slightly (__).
Polar molecules are also known as _______________.
Polarity depends on the __________ and symmetry of the molecule.
symmetrical molecules (looks the same on all sides)= ___________
asymmetrical molecules = ___________
Polar molecules are moved by ____________ charges. (DEMO!) + –
dipole
shape
nonpolar
polar
static

17. a) CH4 b) NH3 c) H2O d) HCl e) BF3
Molecular Polarity
Practice Problems: Determine if the following molecules are polar or nonpolar based on their shape.
a) CH4 b) NH c) H2O d) HCl e) BF3
Dipole of NH3
symmetrical tetrahedral
asymmetrical pyramid
asymmetrical bent
asymmetrical linear
symmetrical trigonal planar
nonpolar
polar
polar
polar
nonpolar

18. Bond Dissociation Energy
This is the energy needed to ___________ the bond.
Generally, the longer the bond, the _____ energy it takes to break it.
Single bonds take ________ energy to break than double bonds and triple bonds require the _________ energy to break.
When bonds form, energy is _____________.
(Breaking bonds requires the addition of energy.)
break
less
less
most
released

19. Intermolecular Attractions
The __________ attractions between one molecule and another are called _______ ______ ________ forces.
They cause gas particles to stick together and _______________ at low temperatures.
weak
Van der Waals
condense

20. Dispersion Forces
There are two types of intermolecular forces:
(1) ____________________ forces: (the weaker type)
caused by random _______________ motion
generally _____________ with ________ electrons in the molecule
Dispersion
electron
stronger
more
− exist between all
types of molecules
− This force causes
Br2 to be a liquid
and I2 to be a solid
at room temperature.

21. Dipole Interaction Forces
(2) ____________ interactions: (the stronger force)
caused by the attraction of the (__) side of one polar molecule and the (__) side of a different polar molecule
Dipole + –

22. Hydrogen Bonds
“________________ Bonds” are a special type of dipole interaction.
They occur between the hydrogen of one polar molecule and the ____, ___ or ___ of another polar molecule.
Hydrogen
N O F
Hydrogen Bonding
in Water

23. Hydrogen Bonds
The ladder rungs in a DNA molecule are hydrogen bonds between the base pairs, (AT and GC).

24. Hydrogen Bonds in DNA