Unit I
Chapters 8 & 9
The “clicker” Review
1
Consider the N−O bond lengths in
nitrite ion and nitrous acid.
(Before you decide, draw a Lewis structure.)
nitrite ion
nitrous acid
within each molecule, the N−O bonds are
1
same length
same length
2
one long one short
one long one short
3
one long one short
same length
4
same length
one long one short
2
2
Consider the N−O bond lengths in
nitrite ion and nitrous acid.
(Before you decide, draw a Lewis structure.)
nitrite ion
nitrous acid
within each molecule, the N−O bonds are
1
same length
same length
2
one long one short
one long one short
3
one long one short
same length
4
same length
one long one short
3
3
Nitrite ions − compared to nitrous acid
•
•
Nitrite ion can resonate
•
same formal charge in both structures
nitrous acid does not resonate
•
•
the formal charge is not the same in both structures
structure on the left, no formal charge at all
..
+1
−1
4
4
Nitrite and nitrate ions − Using “effective number of
bonds” to justify bond lengths
1. FR question 3a
2. Determining the “effective number of bonds”
•
•
•
•
Add the “number of bonds”, double bonds count as 2,
then divide by the number of bonding domains
Nitrite: 3/2 = 1.5
Nitrate: 4/3 = 1.3
•
The smaller the amount of “effective number of bonds”
the longer the bond length. (Inverse association)
5
5
The molecular geometry of SO32− is
(Before you decide, draw a Lewis structure.)
1.
2.
3.
4.
5.
6.
7.
8.
9.
trigonal pyramid
trigonal planar
square planar
tetrahedron
octahedron
T-shaped
see-saw
bent
linear
6
6
The molecular geometry of SO32− is
(Before you decide, draw a Lewis structure.)
26e−
−
− − −
O −S − O
−
−
O
−
−
−
−
trigonal pyramid
trigonal planar
square planar
tetrahedron
octahedron
T-shaped
see-saw
bent
linear
−
1.
2.
3.
4.
5.
6.
7.
8.
9.
tetrahedron domains,
1 unshared pair ∴
trigonal pyramid
7
7
The hybridization around the Si
atom in SiS2 is
(Before you decide, draw a Lewis structure.)
1.
2.
3.
4.
5.
sp
sp2
sp3
3
sp d
sp3d2
8
8
The hybridization around the Si
atom in SiS2 is
(Before you decide, draw a Lewis structure.)
16e−
− Si −
S ＝ ＝S
−
sp
sp2
sp3
3
sp d
sp2d2
−
1.
2.
3.
4.
5.
2 domains,
∴ sp hybridization
9
9
The hybridization around the S
atom in SO2 is
(Before you decide, draw a Lewis structure.)
1.
2.
3.
4.
5.
sp
sp2
sp3
sp3d
sp3d2
10
10
The hybridization around the S
atom in SO2 is
(Before you decide, draw a Lewis structure.)
− − −
O − S＝O
−
−
sp
sp2
sp3
sp3d
sp3d2
−
1.
2.
3.
4.
5.
18e−
3 domains ∴ sp2
11
11
The bond angles in SO3 are
1.
2.
3.
4.
5.
120º
Less than 109.5º
Greater than 109.5º
Less than 120º
Both greater than and less than 120º
12
12
The bond angles in SO3 are
120º
Less than 109.5º
Greater than 109.5º
Less than 120º
Both greater than and less than 120º
−
−
O
O−
− S＝
−
−
−
24e−
−
−
1.
2.
3.
4.
5.
3 domains,
and the unshared pair
bulges and thus takes
up more space
O
−
However, perhaps the resonance that causes equal bond
lengths will also blend the bond angles
13
13
Which of the following molecules are polar?
A) CF4
B) CH3F
C) CH2F2
1.
2.
3.
4.
5.
All of them are polar
Both B + C are polar
Only A is polar
Only B is polar
Only C is polar
14
14
Which of the following molecules are polar?
A) CF4
B) CH3F
C) CH2F2
All of them are polar
Both B + C are polar
Only A is polar
Only B is polar
Only C is polar
−
−
H− C − F
−
F
−
−
−
−
−
−
−
−
−
−
−
−
H− C − F
−
H
−
−
−
F −C− F
−
−
F
−
Remember the shape is
tetrahedron, not a planar
cross, so do NOT place the
F’s opposite in the cross
structure and think that the
polarity crosses out − the
polarity is asymetrically
arranged.
H
H
−
−
−
−
F
−
1.
2.
3.
4.
5.
15
15
The IF2− ion has how many shared
electron pairs, and how many unshared
electron pairs around the central I atom?
1.
2.
3.
4.
5.
2, 1
2, 2
2, 3
3, 1
3, 2
16
16
IF2− ion has how many shared electron
pairs, and how many unshared electron
pairs around the central I atom?
−
F−−
− I
−
−−
−
22e−
−
2, 1
2, 2
2, 3
3, 1
3, 2
−
1.
2.
3.
4.
5.
F
−
17
17
The electron domain geometry on the
central atom of this molecule is
1.
2.
3.
4.
5.
Trigonal planar
Trigonal bipyramid
Tetrahedron
Trigonal pyramid
Linear
18
18
The electron domain geometry on
which this molecule is based is
1.
2.
3.
4.
5.
Trigonal planar
Trigonal bipyramid
Tetrahedron
Trigonal pyramid
Linear
−
The trigonal pyramidal
shape must be caused by
an unshared pair.
19
19
Select the atom(s) below that could
possibly be the central atom of this
molecule. Select all that apply.
1. C
2. P
3. O
4. Al
5. There is no way of knowing
20
20
Select the atom below that could
possibly be the central atom of this
−
molecule.
1. C
2. P
3. O
The unshared pair and three
4. Al
bonding pair mean that the
5. There is no way central atom must have 5
valence electrons.
of knowing
Maybe….it could be C if you
consider the unshared pair to
be a single electron = free
radical
21
21
The shape of the
electron domains in this
molecule can be
Select all that apply.
1.
2.
3.
4.
5.
Trigonal planar with no unshared pairs
Trigonal bipyramid with 2 unshared pairs
Tetrahedron with 1 unshared pair
Trigonal pyramid with 1 unshared pairs
None of the above
22
22
The shape of the
electron domains in this
molecule is most likely
1. Trigonal planar with no unshared pairs
2. Trigonal bipyramid with 2 unshared pairs
• This is not a valid choice because trig bipyr
unshared pairs are in the equatorial positions
not axial, so 2 unshared pair would be T-shape
3. Tetrahedron with 1 unshared pair
4. Trigonal pyramid with 1 unshared pairs
5. None of the above
23
23
Resonance − we draw two (or three) separate Lewis
structures, but really, the molecule is a blend of the
various structures we can draw.
24
24
Which structure(s) below exhibit(s)
resonance structures:
A) CO2 B) NO2− C) SO2
1.
2.
3.
4.
5.
B
C
A & C only
B & C only
A, B, & C
25
25
Which structure(s) below exhibit(s)
resonance structures:
A) CO2 B) NO2− C) SO2
−
−
−
−
−
−
−
−
−
−
−
−
1. B
− − − −
− − −
O − N＝O
O − S＝O
2. C
−
−
−
−
−
−
− − −
3. A & C only
O＝N− O
O＝S− O
−
−
4. B & C only
5. A, B, & C
− C − While you can write a resonance structure
O ＝ ＝O for CO2, with a triple bond and a single
bond, the formal charge is very poor, thus
− C≡
O−
O the resonance structure is not valid.
−
26
26
For each molecule, how many unshared
pair are on each molecule?
1.
2.
3.
4.
5.
0, 0, 1
1, 1, 3
2, 0, 1
2, 1, 3
1, 0, 1
27
27
For each molecule, how many unshared
pairs are on each molecule?
0, 0, 1
1, 1, 3
2, 0, 1
2, 1, 3
1, 0, 1
−
−
1.
2.
3.
4.
5.
−
28
28
What are the total number of
nonbonding pair(s) of electrons on the
central Si atom of SiS2?
1.
2.
3.
4.
5.
1
2
3
4
0
29
29
What are the total number of valence
nonbonding pair(s) of electrons on the
central Si atom of SiS2?
− Si −
S ＝ ＝S
−
1
2
3
4
0
−
1.
2.
3.
4.
5.
30
30
Select the non-polar bond(s) shown
below. Select all that apply.
1.
2.
3.
4.
5.
C−F
C−H
C−O
C−C
C=C
31
31
Select the least polar bond(s)
shown below
1.
2.
3.
4.
5.
•
C-F
C-H this bond is considered nonpolar.
However it is ever SO slightly polar.
C-O
C-C
C=C
Whether single or double, the polarity or
lack there of is calculate in the same
way.
32
32
Draw a Lewis Structure for C2H4F2
1.
Draw as many isomers as you can
33
33
Isomers are:
1.
2.
3.
4.
same chemical structure, different
number of neutrons.
same chemical structure, different
arrangement of electrons.
same chemical formula, but different
arrangement of atoms.
same chemical formula, different
number of electrons.
34
34
Isomers are:
1.
2.
3.
4.
same chemical structure, different
number of neutrons.
same chemical structure, different
arrangement of electrons.
same chemical formula, but different
arrangement of atoms.
same chemical formula, different
number of electrons.
35
35
Draw the structure C2H4F2
Select the number of different
isomers that can exist for C2H4F2
1.
2.
3.
4.
5.
1 structure
2 structures
3 structures
4 structures
5 structures
36
36
Select the number of different
isomers that can exist for C2H4F2
1.
2.
3.
4.
5.
1 structure
2 structures
3 structures
4 structures
5 structures
same
This structure is the same as the
one above it because of free
rotation around the single bond.
37
37
Draw the structure C2H2F2
Select the number of different
isomers that can exist for C2H2F2
1.
2.
3.
4.
5.
1 structure
2 structures
3 structures
4 structures
5 structures
38
38
Select the number of different
isomers that can exist for C2H2F2
1.
2.
3.
4.
5.
1 structure
2 structures
3 structures
4 structures
5 structures
ciscis-1,2 dichloroethene
transtrans 1,2 dichloroethene 1,1 dichloroethene
39
39
Silly Chemistry Jokes
40
Of the 3 isomers that exist for
C2H2F2 how many are polar?
1.
2.
3.
4.
1 structure
2 structures
all 3 structures
none are polar
41
41
Of the 3 isomers that exist for
C2H2F2 how many are polar?
1.
2.
3.
4.
5.
1 structure
2 structures
3 structures
4 structures
5 structures
ciscis-1,2 dichloroethene
transtrans 1,2 dichloroethene 1,1 dichloroethene
42
42
Which of these structures is most polar?
1.
2.
3.
4.
5.
6.
Ortho
ortho
meta
para
Meta
Para
Ortho and meta are equally polar
All three structures are equally polar
None of the structures are polar
43
43
Which of these structures is most polar?
1.
2.
3.
4.
5.
•
Ortho
ortho
meta
para
Meta
Para
Ortho and meta are equally polar
All three structures are polar
This is a planar molecule, and the
molecule will be most polar when the
polar C-Cl bond is oriented in the
same direction.
44
44
Chemistry Humor
45
45
In the molecule HCN, how many σ and
how many π bonds total?
1. 2 σ, 0 π
2. 1 σ, 1 π
3. 2 σ, 1 π
4. 2 σ, 2 π
5. 2 σ, 3 π
46
46
In the molecule HCN, how many σ and
how many π bonds total?
1. 2 σ, 0 π
4. 2 σ, 2 π
5. 2 σ, 3 π
2σ
H− C ≡ N
−
2. 1 σ, 1 π
3. 2 σ, 1 π
2π
47
47
The hybridization of the sulfur
in methyl mercaptan is
1.
2.
3.
4.
5.
•
sp
sp2
sp3
sp3d
sp3d2
methyl mercaptan (also known as ethanethiol) is a
colorless gas with a smell like rotten cabbage. It is
released from animal feces. It occurs naturally in
certain foods, such as some nuts and cheese. It is
also one of the main chemicals responsible for
bad breath and the smell in flatulence. It is added
in very small quantities to CH4, an odorless gas,
so that leaks will be detected.
48
48
The hybridization of the sulfur
in methyl mercaptan is
sp
sp2
sp3
sp3d
sp3d2
There are two unshared
pairs on the S
−
1.
2.
3.
4.
5.
•
−
49
49
Draw a valid Lewis structure for butanol.
How many isomers can be drawn only
making alcohols?
• Enter a number.
50
50
Draw a valid Lewis structure for butanol.
How many isomers can be drawn for this
molecule?
• 4
51
51
Draw a valid Lewis structure for pentane.
How many isomers can be drawn for this
molecule?
• Enter a number.
52
52
Bonding Types
There are two types of elements
metals & nonmetals
thus there are three combinations
metal-nonmetal
metal-metal
nonmetal-nonmetal
53
Bonding in Ionic Compounds (metal & nonmetal)
lattice of ions
• Physical Behavior
•
•
•
hard, rigid, brittle
Electrical Conductivity
•
•
not in solid state, good insulators
yes in both molten and dissolved states
Thermal Conductivity
•
high melting, and even higher boiling
54
54
Bonding in Metals
metal cations (the nucleus and inner core of e−)
surrounded by a “sea of loose delocalized valence e−”
•
•
•
Physical Behavior
•
maleable, ductile
(metal ions slide
about in the e−)
Electrical Conductivity
•
conducts electricity (loose electrons)
Thermal Conductivity
•
•
not as high MP (cations can slide about)
extremely high BP (difficult to break the + − attractions
55
55
Bonding between nonmetals
So just what is a covalent bond?
56
56