Covalent Bonding and Molecular Structure (key)
AX2:
CO2
1. What is the O–C–O bond angle?
180°
2. Which element is more electronegative, carbon, or oxygen?
Oxygen
3. Would you expect CO2 to be a polar or a non-polar molecule? Explain.
Polar. Even though it is composed of polar bonds, the two bonds are located opposite one
another and their affect will cancel each other.
Carbon Dioxide (CO2)
O
C
O
Lewis Dot Structure
O
C
O
Perspective Drawing
Valence Electrons: 16
2
Hybridization: C = sp, O = sp
Electronic Geometry: Linear
Molecular Geometry: Linear
-
2-
AX3:
BF3, NO3 , CO3
1. What is the F–B–F bond angle in BF3?
120°
2. What is the O–N–O bond angle in NO3 ?
120°
23. What is the O–C–O bond angle in CO3 ?
120°
4. Is the electron density in the B-F bond of BF3 oriented closer to fluorine, or to boron?
Fluorine
5. What is the average bond order for the N-O bonds in the nitrate ion?
1
1 /3
6. What is the average bond order for the C-O bonds in the carbonate ion?
1
1 /3
Boron Trifluoride (BF3)
F
F
F
B
Valence Electrons: 24
2
3
Hybridization: B = sp , F = sp
Electronic Geometry: Trigonal Planar
Molecular Geometry: Trigonal Planar
B
F
F
Lewis Dot Structure
F
Perspective Drawing
Nitrate (NO3-)
-
O
O
N
-
O
N
O
O
Lewis Dot Structure
O
Valence Electrons: 24
2
2
Hybridization: N = sp , O = sp
Electronic Geometry: Trigonal Planar
Molecular Geometry: Trigonal Planar
Perspective Drawing
(1 of 3 resonance structures)
Carbonate (CO32-)
2-
O
O
C
O
Lewis Dot Structure
(1 of 3 resonance structures)
2-
O
C
O
O
Perspective Drawing
Valence Electrons: 24
2
2
Hybridization: C = sp , O = sp
Electronic Geometry: Trigonal Planar
Molecular Geometry: Trigonal Planar
AX2E: SO2, SnCl2
1. What is the O–S–O bond angle in SO2?
< 120°
2. What is the Cl–Sn–Cl bond angle in SnCl2?
< 120°
3. Which bond is longer, the S–O bond in SO2 or the Sn–Cl bond in SnCl2? Explain.
Sn – Cl is a longer bond. It is composed of larger atoms, therefore the distance between the
nuclei of the bonded atoms will be greater.
4. Which bond angle would you expect to be smaller, O–S–O or Cl–Sn–Cl? Explain.
The Cl – Sn – Cl will be a smaller bond angel. There are two reasons for this. First, the S –
O bonds are double bonds, so they repel with a greater force and therefore will not be able to
be pushed as close together by the lone pair as the single Sn – Cl bonds in SnCl2. Second,
the Sn – Cl bond is polar resulting in the electron density of those bonds being pulled away
from the Tin resulting in less repulsion and can therefore be pushed closer together.
Sulfur Dioxide (SO2)
O
S
O
Lewis Dot Structure
O
S
O
Perspective Drawing
Valence Electrons: 18
2
2
Hybridization: S = sp , O = sp
Electronic Geometry: Trigonal Planar
Molecular Geometry: Bent
Tin (II) Chloride (SnCl2)
Cl
Sn
Cl
Lewis Dot Structure
Cl
Sn
Cl
Perspective Drawing
Valence Electrons: 18
2
3
Hybridization: S = sp , Cl = sp
Electronic Geometry: Trigonal Planar
Molecular Geometry: Bent
+
AX4:
CH4, NH4 , CH3Cl
1. What is the H–C–H bond angle in CH4?
109.5°
+
2. What is the H–N–H bond angle in NH4 ?
109.5°
3. What is the H–C–Cl bond angle in CH3Cl?
<109.5°
4. What is the H–C–H bond angle in CH3Cl?
>109.5°
5. Which one of these molecules is polar? Using your perspective drawing, draw an arrow
toward the more negative side of the molecule.
Cl
CH3Cl is polar
C
H
H
H
6.
In CH3Cl, which bond is longer, C–H or C–Cl?
C – Cl is a longer bond. This is due to the size of Chlorine versus Hydrogen
Methane (CH4), aka “Carbon tetrahydride”
H
H
C
Valence Electrons: 16
3
Hybridization: C = sp
Electronic Geometry: Tetrahedral
Molecular Geometry: Tetrahedral
H
H
H
H
H
Lewis Dot Structure
C
H
Perspective Drawing
Ammonium (NH4+)
+
H
H
N
H
H
H
H
Lewis Dot Structure
+
H
N
H
Valence Electrons: 8
3
Hybridization: N = sp
Electronic Geometry: Tetrahedral
Molecular Geometry: Tetrahedral
Perspective Drawing
Methyl Chloride (CH3Cl)
Cl
H
C
Cl
H
H
Lewis Dot Structure
H
H
C
H
Perspective Drawing
Valence Electrons: 14
3
3
Hybridization: C = sp , Cl = sp
Electronic Geometry: Tetrahedral
Molecular Geometry: Tetrahedral
+
AX3E: NF3, NH3, H3O
1. What is the F–N–F bond angle in NF3?
<109.5°
2. What is the H–N–H bond angle in NH3?
<109.5°
+
3. What is the H–O–H bond angle in H3O ?
<109.5°
4. Would you expect the electron density from the lone pair to be closer to the nitrogen in NF3,
or in NH3? Explain.
The lone pair will be closer to the nitrogen in NF3. The nitrogen in NF3 is partially positive and
will therefore attract the lone pair more than the partially negative Nitrogen in NH3.
+
5. Which bond angle do you expect to be smaller, F–N–F in NF3 or H–O–H in H3O ? Explain.
The F – N – F bond angle will be smaller. The Fluorine atoms attract electron density away
from the center atom (N) and therefore repel less. The lone pair on the Nitrogen will push the
Fluorine atoms closer together.
Nitrogen Trifluoride (NF3)
Valence Electrons: 26
3
3
Hybridization: N = sp , F = sp
Electronic Geometry: Tetrahedral
Molecular Geometry: Trigonal Planar
F
F
N
N
F
F
F
F
Lewis Dot Structure
Perspective Drawing
Ammonia (NH3)
H
H
N
H
H
H
Lewis Dot Structure
Valence Electrons: 8
3
Hybridization: N = sp
Electronic Geometry: Tetrahedral
Molecular Geometry: Trigonal Planar
N
H
Perspective Drawing
Hydronium (H3O+)
+
H
H
O
H
Lewis Dot Structure
+
H
H
O
H
Perspective Drawing
Valence Electrons: 8
3
Hybridization: O = sp
Electronic Geometry: Tetrahedral
Molecular Geometry: Trigonal Planar
AX2E2: H2O, CH3–O–CH3
1. What is the H–O–H bond angle in H2O?
< 109.5°
2. What is the C–O–C bond angle in CH3-O-CH3?
< 109.5°
3. What is the H–C–H bond angle in CH3-O-CH3?
> 109.5°
+
4. Do you expect the bond angle H–O–H to be smaller in H2O, or in H3O ? Explain.
The H – O – H bond angle in H2O will be smaller. There are two lone pairs pushing the
Hydrogen atoms together which will have a greater affect thatn only one lone pair found in
+
H 3O .
Water (H2O)
H
H
O
Valence Electrons: 20
3
Hybridization: O = sp ,
Electronic Geometry: Tetrahedral
Molecular Geometry: Bent
O
H
H
Lewis Dot Structure
Perspective Drawing
Dimethyl Ether (CH3 – O – CH3)
H
H
C
H
H
O
C
H
H
H
Lewis Dot Structure
H
H
H
C
C
O
H
H
Perspective Drawing
Valence Electrons: 20
3
3
Hybridization: O = sp , C = sp
Electronic Geometry(s):
Carbon – Tetrahedral
Oxygen - Tetrahedral
Molecular Geometry(s):
Carbon – Tetrahedral
Oxygen - Bent
AX5:
PF5, SOF4
1. What is the FA–P– FA bond angle in PF5?
180°
2. What is the FA–P– FE bond angle in PF5?
90°
3. What is the FE–P– FE bond angle in PF5?
120°
4. What is the FE–S– O bond angle in SOF4?
> 120°
5. What is the FA–S– O bond angle in SOF4?
> 90°
6. What is the FE–S– FE bond angle in SOF4?
< 120°
7. What is the FE–S– FA bond angle in SOF4?
< 90°
8. Is the oxygen in SOF4 located in an axial or an equatorial position? Why is this?
Equatorial. The equatorial positions allow for more space to minimize repulsion. For this
reason, the higher repulsion groups (lone pairs, double bonds) will be placed equatorially.
9. Which bond in SOF4 has the shortest bond length?
The S=O will be the shortest. Double bonds are shorter than single bonds.
Phosphorus Pentafluoride (PF5)
F
F
F
F
P
F
F
P
F
F
F
Valence Electrons: 40
3
3
Hybridization: P = sp d, F = sp
Electronic Geometry: Trigonal Bipyramidal
Molecular Geometry: Trigonal Bipyramidal
F
Lewis Dot Structure
Perspective Drawing
Thionyl Tetrafluoride (SOF4)
F
O
F
F
F
S
F
Lewis Dot Structure
F
S
O
F
F
Perspective Drawing
Valence Electrons: 40
3
3
3
Hybridization: S = sp d, F = sp , O = sp
Electronic Geometry: Trigonal Bipyramidal
Molecular Geometry: Trigonal Bipyramidal
+
AX4E: SF4, IF4
1. What is the FA–S– FA bond angle in SF4?
The angle will not be 180°, greater or less than depends on your point of view.
2. What is the FA–S– FE bond angle in SF4?
< 90°
3. What is the FE–S– FE bond angle in SF4?
< 120°
+
4. What is the FA–I– FA bond angle in IF4 ?
The angle will not be 180°, greater or less than depends on your point of view.
+
5. What is the FA–I– FE bond angle in IF4 ?
< 90°
+
6. What is the FE–I– FE bond angle in IF4 ?
< 120°
7. Does the lone pair of electrons in SF4 occupy an axial or an equatorial position? Explain.
The lone pair will occupy an equatorial position. The equatorial positions allow for more
space to minimize repulsion. For this reason, the higher repulsion groups (lone pairs, double
bonds) will be placed equatorially
Sulfur Tetrafluoride (SF4)
F
F
S
Valence Electrons: 34
3
3
Hybridization: S = sp d, F = sp
Electronic Geometry: Trigonal Bipyramidal
Molecular Geometry: Seesaw
F
F
F
S
F
F
F
Lewis Dot Structure
Perspective Drawing
Iodine Tetrafluoride Ion (IF4+)
+
F
F
+
F
F
I
I
F
F
F
Lewis Dot Structure
F
Perspective Drawing
Valence Electrons: 34
3
3
Hybridization: I = sp d, F = sp
Electronic Geometry: Trigonal Bipyramidal
Molecular Geometry: Seesaw
AX3E2: ClF3
1. What is the FA–Cl– FA bond angle in ClF3?
The angle will not be 180°, greater or less than depends on your point of view.
2. What is the FA–Cl– FE bond angle in ClF3?
< 90°
3. Why are you not being asked to predict the FE–Cl– FE bond angle?
There is only one equatorial position occupied, so there is not an FE– Cl–FE to be measured.
4. Which bond do you expect to be longer, FA–Cl or FE–Cl? Explain.
FA
Cl
The FA – Cl bond will be longer. Each of the three bonds
is a polar bond. When a bond is polar it shrinks due to an
increase in ionic character. Since the two FA – Cl bonds
are roughly 180° from one another, the polarity is
cancelled to an extent, and so the bond will shrink less.
There is no opposing polar bond for the FE – Cl so it will be
a more polar and therefore shrink more.
FE
FA
Chlorine Trifluoride (ClF3)
F
F
Cl
F
F
Lewis Dot Structure
Cl
F
F
Perspective Drawing
Valence Electrons: 28
3
3
Hybridization: Cl = sp d, F = sp
Electronic Geometry: Trigonal Bipyramidal
Molecular Geometry: T - Shaped
-
-
AX2E3: I3 , IF2
1. What is the I–I–I bond angle in I3 ?
180°
2. What is the F–I–F bond angle in IF2 ?
180°
3. Which bond length do you expect to be longer, the I–I bond in I3 or the F–I one in IF2 ?
Explain.
I – I bond will be longer. It is composed of larger atoms.
4. Why doesn't either fluorine atom in IF2 occupy an equatorial position?
The equatorial positions allow for more space to minimize repulsion. For this reason, the
higher repulsion groups (lone pairs, double bonds) will be placed equatorially. Since this
molecule contains three lone pairs, each of the lone pairs will occupy the three equatorial
positions.
Triiodide Ion (I3-)
I
-
I
-
I
I
I
I
Lewis Dot Structure
Perspective Drawing
Valence Electrons: 28
Hybridization:
3
I (center) = sp d
3
I (outer) = sp
Electronic Geometry: Trigonal Bipyramidal
Molecular Geometry: Linear
Iodine Difluoride Ion (IF2-)
F
-
F
I
I
F
F
Lewis Dot Structure
-
Perspective Drawing
Valence Electrons: 28
3
3
Hybridization: I = sp d, F = sp
Electronic Geometry: Trigonal Bipyramidal
Molecular Geometry: Linear
AX6:
SF6, IOF5
1. What is the F1–S–F2 bond angle in SF6?
90°
2. What is the F1–S–F3 bond angle in SF6?
180°
3. What is the O–I–F1 bond angle in IOF5?
>90°
4. What is the F1–I–F2 bond angle in IOF5?
<90°
5. What is the F1–I–F5 bond angle in IOF5?
<90°
6. What is the F2–I–F5 bond angle in IOF5?
<90°
7. Are all of the fluorine atoms in SF6 equivalent? Why?
Yes. Each fluorine atom is 90° from four other fluorine atoms and 180° from one other
fluorine.
8. Would you expect angles F1–I–F2 and F2–I–F3 in IOF5 to be equal? Why or why not?
Those angles will be equivalent. F1 and F2 are adjacent to one another, and both are
adjacent to the double bonded oxygen atom. This is also the case for F2 and F3. For this
reason it can be said the bond angles are feeling the same influence.
Sulfur Hexafluoride (SF6)
F
F
F
S
F
F
F
F
F
F
S
F
F
Valence Electrons: 48
3 2
3
Hybridization: S = sp d , F = sp
Electronic Geometry: Octahedral
Molecular Geometry: Octahedral
F
Lewis Dot Structure
Perspective Drawing
Iodine Oxide Pentafluoride (IOF5)
O
F
F
I
F
F
F
Lewis Dot Structure
O
F
F
I
F
F
F
Perspective Drawing
Valence Electrons: 48
3 2
3
3
Hybridization: I = sp d , O = sp , F = sp
Electronic Geometry: Octahedral
Molecular Geometry: Octahedral
-
AX5E: BrF5, TeF5
1. What is the F1–Br–F2 bond angle in BrF5?
<90°
2. What is the F1–Br–F3 bond angle in BrF5?
All that can be said is the angle will not be 180°. To say it is greater than or less than 180°
depends on how you view the molecule. If the molecule were viewed from above according
to figure 3 below the angle would be <180°. If the molecule were viewed from below
according to figure 3 below the angle would be >180°.
F5
F3
F4
Rotate clockwise
90°
F4
F1
Br
F1
F5
F3
Br
F2
Focus on just
F1 – Br – F2 bond
F1
F5
Br
>180
F2
Figure 1
F4
Figure 2
<180
F3
F2
Figure 3
3.
What is the F1–Br–F5 bond angle in BrF5?
<90°
4. What is the F1–Te–F2 bond angle in TeF5 ?
<90°
5. What is the F1–Te–F3 bond angle in TeF5 ?
All that can be said is the angle will not be 180°. To say it is greater than or less than 180°
depends on how you view the molecule. If the molecule were viewed from above according
to figure 3 below the angle would be <180°. If the molecule were viewed from below
according to figure 3 below the angle would be >180°.
F5
F3
F4
Te
F1
Rotate
clockwise
90°
F4
F1
F2
F3
Te
F2
Figure 1
6.
F5
Figure 2
-
What is the F1–Te–F5 bond angle in TeF5 ?
<90°
Focus on
just
F1 – Br – F2
bond
F4
F1
F5
Te
>180
<180
F3
F2
Figure 3
7.
Which bond in BrF5, Br–F1 or Br–F5, do you expect to be longer? Explain.
The Br – F1 bond will be longer than the Br – F5. Each bond is a polar bond. When a bond is
polar it shrinks due to an increase in ionic character. Since the Br – F1 bond has another
equivalent bond oriented roughly 180° from it the polarity is cancelled to an extent, and so the
bond will shrink less. There is no opposing polar bond for the Br – F5 so it will be a more
polar and therefore shrink more.
F5
Rotate
clockwise
90°
F3
F4
Br
F1
F4
F1
F3
Br
F2
F2
Figure 1
8.
F5
Figure 2
Would you expect bond Br–F1 in BrF5 to have a bond length that is shorter, longer, or the
same as the length of bond Te–F1 in TeF5 ? Explain.
The Te – F1 will be a longer bond than Br – F1. This is due to the size of the Tellurium atom
versus the Bromine atom.
Bromine Pentafluoride (BrF5)
F
F
F
F
Br
F
Valence Electrons: 42
3 2
3
Hybridization: Br = sp d , F = sp
Electronic Geometry: Octahedral
Molecular Geometry: Square Pyramidal
F
F
Br
F
F
Lewis Dot Structure
F
Perspective Drawing
Tellurium Pentafluoride Ion (TeF5-)
-
F
F
F
F
Te
F
-
F
F
Te
F
Lewis Dot Structure
F
F
Perspective Drawing
Valence Electrons: 42
3 2
3
Hybridization: Te = sp d , F = sp
Electronic Geometry: Octahedral
Molecular Geometry: Square Pyramidal
-
AX4E2: ICl4
1. What is the Cl1–I–Cl2 bond angle in ICl4 ?
90°
2. What is the Cl1–I–Cl3 bond angle in ICl4 ?
180°
3. Why are the two lone pairs ICl4 on opposite vertices of the molecule?
The lone pairs require more space since they repel more than bonded pairs. For this reason
the two lone pairs will be as far from one another as possible to minimize repulsion.
4. Would you expect Cl1–I to have a shorter, longer, or the same bond length as Cl2–I? Explain.
The bonds will be the same length. The positions of the chlorine atoms (Cl1 and Cl2) are
equivalent to one another.
Iodine Tetrachloride Ion (ICl4-)
Cl
-
Cl
Cl
Cl
Cl
I
Cl
Cl
I
Lewis Dot Structure
Cl
Perspective Drawing
Valence Electrons: 42
3 2
3
Hybridization: I = sp d , Cl = sp
Electronic Geometry: Octahedral
Molecular Geometry: Square Planar