Ch9 Part 2 Dipole Moment

Question 1

Incomplete Octet Examples:

Answer 1

1) BeCl2 - AB2 Linear 180 degrees
2) BF3 - AB3 Trigonal Planar 120 degrees
3) CH4 - AB4 tetrahedral 109.5 degrees
4)PCl5-AB5 Trigonal bipyramidal 90 & 120
6) SF6 - AB6 Octahedral 90 & 90 degrees

Question 2

The ability of an atom to attract electrons in a chemical bond towards itself is?

Answer 2

Electronegativity

Question 3

Molecules with lone pairs on the central atom are labeled?

Answer 3

AByEy
E= # of lone pairs
y = # of atoms

Question 4

Label the types of repulsive forces in each:

1) CH4 - all atoms 109.5 degrees
2) NH3 - 3 atoms / 1 lone PAIR 107.3 deg
3) H2O- 2 atoms / 2 lone pairs 104.5 deg

Answer 4

Types of repulsion:
1) AB4- bonding pair-bonding pair

2) AB3E- bonding pair-bonding pair
& lone pair-bonding pair

3) AB2E2- bonding pair-bonding pair
lone pair-bonding pair
Lone pair-lone pair

Question 5

SO2 Geometry

Answer 5

SO2 Resonance
::O=:S-O::: <—> :::O-S:=O::

Bent Geometry <120 degrees
..
S
// \
O O

Question 6

SF4 Geometry

Answer 6

Sulfur Tetrafluoride SF4 6+7(4)=34 elctrn
..
:F:
.|.
:::F—S—F:::
|
:F:
.. sulfur has an expanded octet

Question 7

Molecular Geometries & Angles

Answer 7

Left side - No lone pairs
Right side - lone pairs

Effects geometry and angles

Question 8

First thing you need to do when determining repulsive forces?

Answer 8

Draw a Lewis Structure

Then: Determine A, B, & E
Then: Predict Geometry

Question 9

Predict the Geometry and Bond Angles of AlF3

Answer 9

Incomplete Octet A=3 + F=7(3)=21 = 24

::F: :F::
\ Al / AB3 - Trigonal Planar
| 120 degrees
:F::

Question 10

Tri iodide

Answer 10

I3-
.. …. ..
:I : :I: I:
.. .. ..

Formal charge
I central - 7bonding-6non -(2be/2) =0
Other atoms
7bonding-6non -(4be/2=2) = -1
I-

Question 11

The ability of an atom to attract electrons in a chemical bond towards itself is called?

Answer 11

Electronegativity

Question 12

When a compound is made up of 2 of the same atoms where electrons are shared equally it is a?

Answer 12

Non-polar covalent bond
Ex.
H—H or F—F

Question 13

When a compound is made up of 2 different atoms and electrons are shared but ARE NOT SHARED EQUALLY, it is a?

Answer 13

Polar covalent bond -
electrons are NOT shared equally!

Ex.
H—F

Question 14

When electrons spend more time in the vicinity of 1 atom than the other, this creates a ?

Answer 14

Polar bond

Question 15

3 types of bonding are?

Answer 15

Pure Covalent- electrons are equidistant from the atoms
Polar Covalent- electrons shared unequally creating partially + or - properties on the atoms with more or less electrons
Ionic - electron transfer (cation+ anion-)

Question 16

Measures how polar a bond is

Answer 16

Dipole moment - how much pull 1 atom has over the other in a covalent bond

Question 17

What do we use to measure dipole moments?

Answer 17

Vectors (arrows —-> or <—-)

Question 18

What pieces of information do vectors give us?

Answer 18

Direction and magnitude

1) Direction -
From the least electromagnetic to most

2) Magnitude - length of vector

Question 19

Diatomic molecules made up of the same element create what type of bond?

Answer 19

Nonpolar covalent

Question 20

Diatomic molecules made up of different elements create what type of bond?

Answer 20

Polar covalent

Question 21

When molecules are made up of three or more elements what things must be taken into account?

Answer 21

Polarity of the bond and molecular geometry

Question 22

Molecules made up of 3 atoms can be one of two types of geometry, which are?

Answer 22

Linear B—A—B Or

Bent A
/ \
B B

Question 23

Vectors always point from__________ to the __________?

Answer 23

Vectors point from the least electronegative atom to the most electronegative atom 

Question 24

If B is more electro negative than a in the linear geometry of an atom, where do the vectors point?

Answer 24

From A to B

Question 25

When the atoms are the same, what are the magnitudes of the vectors pointing to those atoms?

Answer 25

When the atoms are the same, the vectors magnitude & length are the same

Question 26

Each vector by itself is called a ?

Answer 26

Bond moment

Question 27

The actual dipole moment is the ?

Answer 27

Sum of the individual bond moments

Question 28

Dipole moment is the

Answer 28

Sum of individual bond moments being reinforced with a polar covalent bond

Question 29

The second vector is always drawn

Answer 29

Where the first vector ends

Question 30

In order for vectors to cancel they must create a non-polar covalent bond with bonds of ?

Answer 30

The same length & magnitude There is NO DIPOLE MOMENT when bonds cancel

Question 31

When dipoles do not end in the same spot they started, as in a bent structure, this creates a _____, where vectors do not cancel but give us a sum of where they started to where they ended

Answer 31

Dipole moment -The purple line, in the picture below, connecting the 2 red dipoles represents the sum of the 2 dipoles that is creating the dipole moment —————————- These vectors don’t cancel, they reinforce

Question 32

When a dipole moment is created, the bonds are?

Answer 32

Reinforced

Question 33

When 2 vectors are reinforced in a polar covalent molecule, this creates a ?

Answer 33

dipole moment

Question 34

What must be done properly to determine proper bond moments?

Answer 34

The proper Lewis structure using the correct geometry is needed in order to determine proper bond moments

Question 35

With linear geometry, ? However with bent geometry?

Answer 35

Linear - Vectors cancel and there is no dipole moment Bent- the vectors reinforce each other and you have a dipole moment

Question 36

Can vectors point to lone pair bonds?

Answer 36

No they only point from atom to atom

Question 37

Linear = Bent =

Answer 37

Linear = 2 bond moments that cancel for no dipole moment Bent = 2 bond moments that reinforce and create a dipole moment

Question 38

What can be used to differentiate between ISOMERS (compounds with the same formula but different structures) like C2H2Cl2?

Answer 38

Dipole moments can be used to differentiate between isomers (compounds with the same formula but different structures) like in C2H2Cl2 In the picture: Dipole moment (left) polar / no dipole (right) non-polar

Question 39

Dipole moment =

Answer 39

Vector Sum of all Bond Moments