Welcome to Chem 1C with
Terri Bentzinger
E-mail: [email protected]
Website: http://clas.sa.ucsb.edu/staff/terri/
Drop-in: M/T/W/R 1-2 pm ⇒ SRB Rm 3274
Bonding
– ch. 13/14
Chem 1C is Very conceptual – lots of memorizing
Bonding
– ch. 13/14
1. Rank the following bonds in order of least polar to most polar:
C-N C-O C-H C-Br
Bonding
– ch. 13/14
Bond Polarity ⇒ uneven distribution of bonding electrons due to a
difference in electronegativity
Red ⇒ high
electron
density
Purple⇒ low
electron
density
H⇒ 2.2
F⇒ 4.0
Bonding
– ch. 13/14
2. For each of the following draw the Lewis structure, determine the
electronic and molecular geometries, predict the bond angle, state
if polar or non polar and label the hybridization on the central
atom.
a. BeF2
b. HCN
c. SO2
d. PCl3
e. SF6
f. XeI5+
g. ICl4-
Bonding
– ch. 13/14
3. Place the following molecules in order from smallest to largest
H−N−H bond angles:
NH4+
NH3
NH2–
Bonding
– ch. 13/14
4. Rank the following in order of shortest to longest carbon-oxygen
bond length:
CO32-
CO2
CO
CH3OH
Bonding
– ch. 13/14
5. Which of the following shows these molecules in order from most
polar to least polar?
CH4 , CF2Cl2 , CF2H2 , CCl4 , CCl2H2
A) CH4 > CF2Cl2 > CF2H2 > CCl4 > CCl2H2
B) CH4 > CF2H2 > CF2Cl2 > CCl4 > CCl2H2
C) CF2Cl2 > CF2H2 > CCl2H2 > CH4 = CCl4
D) CF2H2 > CCl2H2 > CF2Cl2 > CH4 = CCl4
E) CF2Cl2 > CF2H2 > CCl4 > CCl2H2 > CH4
Bonding
– ch. 13/14
6. For the following structures:
a. Fill in the missing bonds/electrons (if any)
b. Label the hybridization for the carbons, nitrogen and oxygen atoms
c. Assign the indicated angles
d. Determine the number of sigma (σ) and pi (π) bonds
e. Describe the indicated bonds
i
j
l
m
k
Bonding
– ch. 13/14
7. Which of the following resonance contributors for N2O is the most
stable? Hint: calculate formal charges
Bonding
– ch. 13/14
8. Will all of the atoms in allene lie in the same plane?
Bonding
– ch. 13/14
9. Fill in the following table:
Molecule/Ion
H2
He2+
B2
CN–
O2
Electron
Configuration
Bond Order
Magnetism
Bonding
– ch. 13/14
Molecular orbitals
S with S
P with P
Bonding
– ch. 13/14
MO diagram for homonuclear
molecules in Groups 1-5
MO diagram for homonuclear
molecules in Groups 6-8
Bonding
– ch. 13/14
σ2p*
π2p*
σ2p*
π2p
π2p*
σ2p
σ2p
π2p
σ2s*
σ2s
Alligators Like to eat Beef BaCoN
Period 2, groups 1-5
σ2s*
σ2s
Hatchets chop OFf at the kNee
Period 2, groups 6-8
Bonding
– ch. 13/14
10. Label the following molecular orbitals.
A.
D.
B.
C.
E.
Bonding
– ch. 13/14
11. Identify the element X if the ion X2- has the following valence
electron configuration; (σ3s)2(σ3s*)2(π3p)4(σ3p)2(π3p*)1
Bonding
– ch. 13/14
12. Using the MO model predict the relative bond dissociation energy
for the following:
F2
F2F 2+
Bonding
– ch. 13/14
You have completed ch. 14
Bonding
– ch. 13/14 – Answer Key
1. Rank the following bonds in order of least polar to most polar:
C-N C-O C-H C-Br
C-H < C-Br < C-N < C-O
Bonding
– ch. 13/14 – Answer Key
2. For each of the following draw the Lewis structure, determine the
electronic and molecular geometries, predict the bond angle, state
if polar or non polar and label the hybridization on the central
atom.
a. BeF2 => EG/MG-linear, 180º, non-polar, sp
b. HCN => EG/MG-linear, 180º, polar, sp
c. SO2 => EG-trigonal planar, MG-bent, 120º, polar, sp2
d. PCl3 => EG-tetrahedral, MG-trigonal pyramid, <109º, polar, sp3
e. SF6 => EG/MG-octahedral, 90º, non-polar, d2sp3 or sp3d2
f. XeI5+ => EG-octahedral, MG-square pyramid, 90º, polar, d2sp3 or sp3d2
g. ICl4- => EG-octahedral, MG-square planar, 90º, non-polar, d2sp3 or sp3d2
Bonding
– ch. 13/14 – Answer Key
3. Place the following molecules in order from smallest to largest
H−N−H bond angles:
NH4+
NH3
NH2–
NH2– < NH3 < NH4+
4. Rank the following in order of shortest to longest carbon-oxygen
bond length:
CO32CO2
CO
CH3OH
CO < CO2 < CO32- < CH3OH
5. Which of the following shows these molecules in order from most
polar to least polar?
D) CF2H2 > CCl2H2 > CF2Cl2 > CH4 = CCl4
Bonding
– ch. 13/14 – Answer Key
6. For the following structure:
a. Fill in the missing bonds/electrons (if any) each nitrogen is missing 1 lone
pair and each oxygen is missing 2 lone pairs
b. Label the bonds as sigma (σ) or pi (π) single bonds are sigma, double
bonds have one sigma and one pi, triple bonds have one sigma and two pi
c. Label the hybridization for the carbons, nitrogens and oxygens.
d. Assign the bond angles
sp3
sp2
sp
sp2
sp2
sp2
sp3
sp3
a. < 109.5°
b. 120°
c. <120°
d. 120°
e. 180°
f. 120°
g. <109.5°
h. 109.5°
Bonding
– ch. 13/14 – Answer Key
7. Which of the following resonance contributors for N2O is the most
stable? Hint: calculate formal charges
F.C. = 5-3-2 = 0
F.C. = 5-2-4 = -1
F.C. = 5-4-0 = +1
F.C. = 6-2-4 = 0
F.C. = 5-1-6 = -2
F.C. = 5-4-0 = +1
F.C. = 6-1-6 = -1
F.C. = 5-4-0 = +1
F.C. = 6-3-2 = +1
Most stable ⇒
Minimum magnitude of F.C.
and
(-) F.C. on most EN atom
Bonding
– ch. 13/14 – Answer Key
8. Will all of the atoms in allene lie in the same plane? No
Since pi is y then it’s
sp2xz
π can’t be x
so let’s say y
Since pi is z then it’s
sp2xy
if central C
is spx
all 3 Cs are
on the x axis
π can’t be x or y
so z
Bonding
– ch. 13/14 – Answer Key
9.
Molecule
Electron Configuration
Bond Order
Magnetism
H2
(σ1s)2
1
diamagnetic
He2+
(σ1s)2(σ1s*)1
0.5
paramagnetic
B2
(σ2s)2(σ2s*)2
0
paramagnetic
CN-
(σ2s)2(σ2s*)2(π2p)4(σ2p)2
3
diamagnetic
O2
(σ2s)2(σ2s*)2(σ2p)2(π2p)4(π2p*)2
2
paramagnetic
10. a. σ1s* or σ2s*
11. P
12. F2+ > F2 > F2-
b. σ2p
c. π2p*
d. σ1s or σ2s
e. π2p