Chemistry Chapter 5

Front 1

What does VSEPR stand for?

Back 1

Valence Shell Electron Pair Repulsion

Front 2

Who was G.N. Lewis?

Back 2

An American chemist from the University of California - Berkeley, who constructed a theoretical model about chemical bonding.

Front 3

The Lewis Model focused on three things. What is the first thing it focused on?

Back 3

Valence electrons are most important in chemical bonding.

Front 4

The Lewis Model focused on three things. What is the second thing it focused on?

Back 4

Valence electrons are transferred from one atom to another to form ionic bonds, or shared between atoms to form covalent bonds.

Front 5

The Lewis Model focused on three things. What is the third thing it focused on?

Back 5

When valence electrons are transferred or shared, the atoms in the compound form full outer Bohr orbits and therefore gain stable electron configurations.

Front 6

A stable electron configuration usually involves eight electrons. This is known as what?

Back 6

The octet rule.

Front 7

A stable configuration for both Hydrogen and Helium is called what?

Back 7

A duet.

Front 8

In the lewis theory, what do we use to represent valence electrons?

Back 8

Dots

Front 9

The Lewis structure of an element is its _________ _________ surrounded by _____ to represent __________ __________.

Back 9

Chemical Symbol

Dots

Valence Electrons

Front 10

T/F In the Lewis theory, we represent both the core or inner electrons and the valence electrons with dots surrounding the chemical symbol for the element.

Back 10

False, we ignore the inner or core electrons and represent the valence electrons with dots surrounding the chemical symbol for the element.

Front 11

Draw a Bohr model and a Lewis model for Silicon (Atomic number: 14).

Back 11

Front 12

Draw the Lewis structures for: C, H, He, Na, Mg, N, O, Ne.

Back 12

Front 13

T/F With Lewis structures, there are a maximum of four dots per side of a Chemical symbol.

Back 13

False, there are a maximum of two dots per side.

Front 14

T/F According to Lewis theory, chemical bonding brings elements together in the correct ratios so that, either by transferring or by sharing electrons, all the atoms involved form an octet.

Back 14

True

Front 15

Based on the Lewis structures for hydrogen and helium, explain why buoyant balloons are filled with helium instead of hydrogen gas, even though hydrogen gas is cheaper and more buoyant.

Back 15

Helium is stable, whereas hydrogen is unstable and looking to react with anything to become stable, which makes it dangerous.

Front 16

In Lewis theory, we combine the Lewis structure of elements to form Lewis structures for _________.

Back 16

Compounds

Front 17

With Lewis structures, we represent ionic bonding by doing what?

Back 17

Moving dots from the Lewis structure of the metal to the Lewis structure of the nonmetal.

Front 18

Draw what this becomes.

Back 18

Front 19

Draw what this becomes.

Back 19

Front 20

When showing ionic bonds in the Lewis structure, the metal and the nonmetal each acquire a charge, therefore we indicate what in the upper right corner of the symbol?

Back 20

We indicate the magnitude of the charge.

Front 21

When showing ionic bonds in the Lewis structure, we enclose the anion in what to show that the charge belongs to the entire chlorine assembly, including the electron "dots?"

Back 21

We enclose the anion in brackets.

Front 22

Draw the Lewis structure for the ionic compound MgO.

Back 22

Front 23

Draw the Lewis structure for the ionic compound SrCl2.

Back 23

Front 24

What is the Lewis structure and chemical formula for the compound between Calcium and Fluorine?

Back 24

The chemical formula is CaF2.

Front 25

What is the Lewis structure and chemical formula for the compound between Lithium and Oxygen?

Back 25

The chemical formula is Li2O.

Front 26

In covalent bonds, atoms do what with their electrons?

Back 26

Share them

Front 27

In ionic bonds, atoms do what with their electrons?

Back 27

Transfer them

Front 28

T/F In covalent bonds, some dots count for the octet of more than one atom.

Back 28

True

Front 29

Draw the Lewis structure for Cl2.

List the Bonding pair electrons.

List the Lone pair electrons.

Back 29

Front 30

In a covalent bond, the electron pair between two atoms are called what?

Back 30

Bonding pair electrons.

Front 31

In a covalent bond, the electron pairs on a single atom are called what?

Back 31

Lone pair electrons.

Front 32

T/F Bonding electrons count toward the octet of both atoms. Lone pair electrons only count toward the octet of the atom they are on.

Back 32

True

Front 33

This is an example of what?

Back 33

An Ionic bond lattice.

Front 34

Fluorine, Bromine, and Iodine exist as diatomic molecules in nature. Explain why using Lewis structures.

Back 34

Front 35

T/F We can simplify our notations by representing bonding electron pairs with dashes.

Back 35

True

Front 36

Draw the Lewis structure for H20.

Back 36

Front 37

Draw the Lewis structure for CCl4.

Back 37

Front 38

Can atoms share more than one electron pair to form complete octets?

Whats an example of this?

Back 38

Yes

O2

Front 39

Draw the Lewis structure for O2.

Back 39

Front 40

In Lewis structures, two bonding pairs together is called what?

Back 40

A double bond.

Front 41

In Lewis structures, can atoms share three electron pairs to form complete octets?

Back 41

Yes

Front 42

Double bonds are _________ and _________ than single bonds because the bond contains twice as many electrons.

Back 42

Shorter

Stronger

Front 43

Draw the Lewis structure for N2.

Back 43

Front 44

In Lewis structures, three bonding pairs together is called what?

Back 44

A triple bond.

Front 45

Triple bonds are ________ and _________ than either single or double bonds.

Back 45

Shorter

Stronger

Front 46

What are the four steps for writing Lewis structures?

Back 46

1. Write the skeletal structure of the molecule.

2. Determine the total number of electrons for the molecule. (final product will have this same number)

3. Place the electrons as dots to give octets to as many atoms as possible. (start with single bonds)

4. If the central atoms has not obtained an octet, form double or triple bonds as necessary to give it an octet.

Front 47

Draw the Lewis structure for NH3.

Back 47

Front 48

Draw the Lewis structure for PCl3.

Back 48

Front 49

Draw the Lewis structure for H2CO.

Back 49

Front 50

Draw the Lewis structure for CO2.

Back 50

Front 51

Draw the Lewis structure for HCN.

Back 51

Front 52

Draw the Lewis structure for HC2H.

Back 52

Front 53

Suppose that when drawing a Lewis structure for a molecule, you end up with a structure in which the central atom lacks an octet. What should you do?

a. Add more electrons to give the central atom an octet.

b. Remove the central atom from the Lewis structure.

c. Move a lone pair from a terminal atom to a lone pair position on the central atom.

d. Form a multiple bond by moving a lone pair from a terminal atom to the bonding region between the terminal atom and the central atom.

Back 53

D

Front 54

What is resonance?

What is it represented by?

Back 54

The averaging of two identical Lewis structures.

By Resonance structures.

Front 55

Draw an example of a resonance structure.

Back 55

Front 56

The averaging of two identical Lewis structures is called __________ and is usually represented by drawing both structures - called ___________ __________ - with a double-headed arrow between them.

Back 56

Resonance

Resonance Structures

Front 57

Draw the Lewis structures for O3.

Back 57

Front 58

Each bond in O3 is like what?

Back 58

Like a bond and a half.

Front 59

What is O3?

Back 59

Ozone

Front 60

T/F Real ozone molecules have two identical bonds (equal length and strength). Each bond is shorter than a single bond, but longer than a double bond. Each bond in ozone is like a bond and a half.

Back 60

True

Front 61

O2 has what kind of bond?

Back 61

Double bond

Front 62

Which has stronger bonds, O2 or O3?

Back 62

O2

Front 63

Why is it important that O3 makes up the atmosphere instead of O2?

Back 63

The bonds in O3 molecules are weaker than the bonds in O2 molecules meaning that if the atmosphere is made up of O3 molecules, harmful UV light will be able to be absorbed in a chemical reaction by the O3 molecules with the weaker bonds, whereas O2 bonds are too strong to be able to react with the UV light, allowing that light to pass through the atmosphere where it can cause harm.

Front 64

T/F VSEPR theory is based on the idea that the negative charges of bonding electrons and lone pair electrons in a molecule repel each other, and that these repulsions determine the shape of the molecule.

Back 64

True

Front 65

The geometry of a molecule is determined by what?

Back 65

By maximizing the distance between all electron groups on the central atom(s) of the molecule.

Front 66

T/F Molecules can only be two-dimensional.

Back 66

False, molecules can be three dimensional.

Front 67

What is the difference between electron geometry and molecular geometry?

Back 67

Electron geometry is the geometry of the two-dimensional lewis structure and molecular geometry is the three-dimensional shape of a molecules atoms.

Front 68

An electron group may be one of four things. What are the four things?

Back 68

Lone pair

Single bond

Double bond

Triple bond

Front 69

What can a bonding group be?

Back 69

A single, double, or triple bond.

Front 70

What is the electron and molecular geometry of H2S?

Back 70

Front 71

What is the electron and molecular geometry of PCl3?

Back 71

Front 72

What is the electron and molecular geometry for the following?

Total Electron Groups: 2

Bonding Groups: 2

Lone Pairs: 0

Back 72

Electron Geometry: Linear

Molecular Geometry: Linear

Front 73

What is the electron and molecular geometry for the following?

Total Electron Groups: 3

Bonding Groups: 3

Lone Pairs: 0

Back 73

Electron Geometry: Trigonal planar

Molecular Geometry: Trigonal planar

Front 74

What is the electron and molecular geometry for the following?

Total Electron Groups: 3

Bonding Groups: 2

Lone Pairs: 1

Back 74

Electron Geometry: Trigonal planar

Molecular Geometry: Bent

Front 75

What is the electron and molecular geometry for the following?

Total Electron Groups: 4

Bonding Groups: 4

Lone Pairs: 0

Back 75

Electron Geometry: Tetrahedral

Molecular Geometry: Tetrahedral

Front 76

What is the electron and molecular geometry for the following?

Total Electron Groups: 4

Bonding Groups: 3

Lone Pairs: 1

Back 76

Electron Geometry: Tetrahedral

Molecular Geometry: Trigonal pyramidal

Front 77

What is the electron and molecular geometry for the following?

Total Electron Groups: 4

Bonding Groups: 2

Lone Pairs: 2

Back 77

Electron Geometry: Tetrahedral

Molecular Geometry: Bent

Front 78

What is the electron and molecular geometry for SiH4?

Back 78

Electron geometry: Tetrahedral

Molecular geometry: Tetrahedral

Front 79

What is the electron and molecular geometry for CF2Cl2?

Back 79

Electron geometry: Tetrahedral

Molecular geometry: Tetrahedral

Front 80

T/F A double or triple bond acts like a bonding electron pair (or a single bond) in determining molecular geometry.

Back 80

True

Front 81

Why is the molecular geometry of CO2 linear?

Back 81

Because their are double bonds on either side of the carbon atom, they must stay together and act like a group. The two groups minimize their repulsion by getting as far away from each other as possible, resulting in a linear geometry. Their are no lone pairs on the central atom.

Front 82

What is the electron and molecular geometry for SO2?

Back 82

Electron geometry: Trigonal planar

Molecular geometry: Bent

Front 83

What is the electron and molecular geometry for H2CS?

Back 83

Electron geometry: Trigonal planar

Molecular geometry: Trigonal planar

Front 84

Draw the Lewis structure and then the molecular geometry for C2H4.

Back 84

Trigonal planar about each carbon.

Front 85

Draw the Lewis structure and then the molecular geometry for C2H2.

Back 85

Linear.

Front 86

Carbon dioxide and water are both composed of a central atom that bonds to two other atoms, yet carbon dioxide is a linear molecule, whereas water is bent. Why?

Back 86

Carbon dioxide has two double bonds and no lone pairs on the central atom, making it linear. Water has two single bonds and two lone pairs on the central atom, making it bent. The lone pairs on the central oxygen in water cause the bent geometry.

Front 87

What is a dipole?

Back 87

A dipole is when a covalent bond develops two poles, one positive and one negative.

Front 88

What is a polar bond?

Back 88

A covalent bond with uneven electron distributions.

Front 89

Why do polar bonds occur?

Back 89

They occur because one side of a covalent bond, the side that is electron deficient, develops a slight positive charge, whereas the other side of the bond, the side that is electron rich, develops a slight negative charge.

Front 90

What is electronegativity?

Back 90

The ability of an atom to attract electrons in a covalent bond.

Front 91

Which element is the most electronegative?

Back 91

Fluorine

Front 92

Elements with the highest electronegativities are located where on the periodic table?

Back 92

The top-right corner.

Front 93

Elements with the lowest electronegativities are located where on the periodic table?

Back 93

The bottom-left corner.

Front 94

T/F Electronegativity increases as you go to the right across a row on the periodic table and decreases as you go down a column.

Back 94

True

Front 95

T/F A covalent bond between two atoms of similar electronegativities will be polar.

Back 95

False, A covalent bond between two atoms of differing electronegativities will be polar.

Front 96

T/F The greater the difference in electronegativity is, the more polar the bond will be.

Back 96

True

Front 97

T/F Identical atoms, or atoms of equal electronegativity, form polar bonds.

Back 97

False, Identical atoms, or atoms of equal electronegativity, do not form polar bonds - they share their electrons equally.

Front 98

T/F An entire molecule may be a polar molecule if it has an uneven electron distribution that results in a negative pole and a positive pole.

Back 98

True

Front 99

Draw the diagram for Carbon Monoxide's electronegativity.

Back 99

Front 100

What happens to opposing dipoles that are found in a linear molecule?

Back 100

Their charges cancel each other out.

Front 101

T/F Polar bond will not always give rise to polar molecules.

Back 101

True

Front 102

Would a bond between two atoms of the same element be polar? Why or why not?

Back 102

It would not be polar because the atoms have the same electronegativity and therefore share electrons in the bond equally.

Front 103

T/F A nonpolar molecule does not have a charge separation the way a polar one does.

Back 103

True

Front 104

T/F Polar bonds result in polar molecules unless the symmetry of the molecule is such that the polar bonds cancel.

Back 104

True

Front 105

Is water polar or non polar? Why?

Back 105

Polar. Its structure is bent meaning that the two similar bonds don't cancel each other out.

Front 106

Draw the diagram for water's electronegativity.

Back 106

Front 107

In a polar molecule, the ___________ _____ of the molecule attracts the ___________ ______ of its neighbor.

Back 107

Positive end

Negative end

Front 108

LINEAR

Two identical polar bonds pointing in opposite directions do what?

The molecule is therefore what?

Back 108

Cancel each other out.

Nonpolar

Front 109

BENT

Two polar bonds with an angle of less than 180º between them will do what?

The molecule is therefore what?

Back 109

Not cancel each other out.

Polar

Front 110

TRIGONAL PLANAR

Three identical polar bonds at 120º from each other will do what?

The molecule is therefore what?

Back 110

Cancel each other out.

Nonpolar

Front 111

TETRAHEDRAL

Four identical polar bonds in a tetrahedral arrangement will do what?

The molecule is therefore what?

Back 111

Cancel each other out.

Nonpolar

Front 112

TRIGONAL PYRAMIDAL

Three polar bonds in pyramidal arrangement will do what?

The molecule is therefore what?

Back 112

Not cancel each other out.

Polar

Front 113

Water would be a gas at room temperature if not for what?

Back 113

The attraction between the positive and negative ends of water molecules which are polar in nature.

Front 114

T/F Oil and water don't mix because water is polar and therefore attracted to other polar molecules and oil is non polar.

Back 114

True

Front 115

We can tell whether simple molecules are polar or non polar by looking at their Lewis structures and asking what two questions?

Back 115

Does the molecule contain polar bonds?

Do the polar bonds add together to give overall polarity to the molecule?

Front 116

Is CF4 polar or non polar?

Back 116

Nonpolar

Front 117

Is SCl2 polar or non polar?

Back 117

Polar

Front 118

The structure of ice consists of water molecules in what kind of arrangement?

Back 118

A hexagonal arrangement.

Front 119

Can a molecule composed of two different atoms with different electronegativities be non polar?

Back 119

No, because the molecule has only one polar bond, there can be no other bonds to cancel its polarity.

Front 120

We have seen how the shape of water molecules determines the properties of water. If the molecule had a different shape, water would be a different substance. Suppose the shape of water were different in a way that resulted in ice being denser than liquid water. How would a cup of ice look? Would icebergs exist? What would happen to marine life in winter as ice formed in lakes?

Back 120

If ice were denser than liquid water, it would sink. Icebergs would not exist. As water froze in a lake or ocean, it would sink to the bottom, probably killing marine life.