Chapter 3: 3.1 Ionic and Covalent Bonding

Question 1

True or False:
Only core electrons participate in bonding

Answer 1

False, only valence electrons participate in bonding

Question 2

Elements of low electronegativity typically form:

Answer 2

Ionic bonds

Question 3

Elements of moderate electronegativity typically form:

Answer 3

Covalent bonds

Question 4

Elements of higher electronegativity can form:

Answer 4

Covalent or Ionic bonds

Question 5

True or False:
In an ionic bond, the two atoms share electrons equally

Answer 5

False, this is due to the large difference in negativity between the two atoms

Question 6

When is a bond considered ionic?

Answer 6

When there is a complete transfer of an electron from the atom of lower electronegativity to the atom with the higher electronegativity

Question 7

At what difference in electronegativity do ionic bonds occur?

Answer 7

Greater than 1.9

Question 8

Compounds that have ionic bonds have what properties?

Answer 8

High melting points
Crystal lattices

Question 9

What can Coulomb’s law determine?

Answer 9

The magnitude of the attractive force between anions and cations

Question 10

Scenario:
When ions get bigger, what will happen?

Answer 10

Spacing between ions gets bigger
Weaker force of attraction (changes melting points etc.)

Question 11

Covalent bonds involve _______ of electrons

Answer 11

Sharing

Question 12

True or False:
The electrons in covalent bonds are always shared equally

Answer 12

False

Question 13

At what difference in electronegativity is the sharing of electrons in covalent bonding deemed unequal?

Answer 13

Less than 1.9, greater than 0.5

Question 14

What are covalent bonds with unequal sharing of electrons known as?

Answer 14

Polar covalent bonds (Polar bond, for short)

Question 15

What do polar bonds give rise to?

Answer 15

Dipole moment

Question 16

The greater the difference in electronegativity, the ______ the magnitude of the dipole moment

Answer 16

Larger

Question 17

Dipole moment should be drawn:

Answer 17

Either way, as long as you are consistent
Positive to negative (electron pull)
Negative to positive (IUPAC)

Question 18

What is used to show dipole moment?

Answer 18

Electrostatic Potential Maps

Question 19

What do the colors on an Electrostatic Potential Map represent?

Answer 19

Red: Negative
Blue: Positive

Question 20

What are covalent bonds with approximately equal sharing of electrons known as?

Answer 20

Nonpolar covalent bonds

Question 21

At what difference in electronegativity do nonpolar covalent bonds occur?

Answer 21

0.5 or less

Question 22

Why are bonds with an electronegativity difference of 0.5 or lower called “nonpolar covalent bonds”?

Answer 22

They have virtually no permanent dipole movements

Question 23

Define:
Lewis structure

Answer 23

A diagram showing the atoms, the covalent bonds, the lone electron pairs, and any charges that may be present on the atoms

Question 24

True or False:
Lewis structures show the molecular shape of a molecule

Answer 24

False, Lewis structures are not intended to show or imply molecular shape

Question 25

Define:
Formal Charge

Answer 25

The difference between the number of electrons “owned’ by that atom in the Lewis structure and the number of valence electrons in a free atom of the same element in its neutral state

Question 26

What is the number of electrons “owned” by an atom?

Answer 26

The nonbonding electrons, along with half the electrons in the covalent bonds formed by the atom

Question 27

Define:
Octet Rule

Answer 27

If there are enough valence electrons in the molecule, then all of the second-row (2nd row p-block elements) atoms C, N, O, F, Ne must have 8 valence electrons

Question 28

Does the Octet Rule apply to Li and Be? How about B?

Answer 28

Li and Be usually do not form covalent bonds, so the Lewis theory is rarely applied to them

Boron-containing compounds usually do not have enough valence electrons for B atoms to satisfy the octet rule

Question 29

True or False:
Atoms in the second row sometimes have more than 8 electrons in a Lewis Structure

Answer 29

False, C, N, O, F, and Ne atoms can never have more than 8 electrons in a Lewis structure

Question 30

Lewis Structure Procedure:
Step 1

Answer 30

Count total number of valence electrons in molecule by adding valence electrons of each neutral atom
Add one for each negative charge, subtract one for each positive charge

Question 31

Lewis Structure Procedure:
Step 2

Answer 31

Draw a skeleton structure, joining atoms together by single bond
Usually element with lowest electronegativity is the central atom

Question 32

Lewis Structure Procedure:
Step 3

Answer 32

Count the number of single bonds drawn and calculate the number of valence electrons in the bonds

Question 33

Lewis Structure Procedure:
Step 4

Answer 33

Distribute the remaining valence electrons among the atoms

Question 34

Lewis Structure Procedure:
Step 5

Answer 34

Assign formal charges to all atoms and check their sum

Question 35

How do we choose the best Lewis structure?

Answer 35

The best is normally the structure in which the formal charges are the smallest and consistent with the relative electronegativities of the atoms

Question 36

Define:
Resonance structures

Answer 36

Multiple correct Lewis structures that differ only in the positions of the electrons and multiple bonds

Question 37

How are resonance structures best represented?

Answer 37

Resonance hybrids

Question 38

Define:
Average bond order

Answer 38

Average number of bonds between specific atoms

Question 39

Line Diagrams, True or False:
Each solid line represents an ionic bond

Answer 39

False, each solid line represents a covalent bond

Question 40

Line Diagrams, True or False:
If no atom is draw at the intersection of two lines, it is assumed to be a carbon atom

Answer 40

True

Question 41

If no atom is drawn at the end of a line, what is it assumed to be?

Answer 41

A carbon atom

Question 42

Line Diagrams, True or False:
Hydrogen atoms bonded to carbons are shown

Answer 42

False

Question 43

Line Diagrams, True or False:
All non-carbon atoms must be drawn along with hydrogens that are attached to them

Answer 43

True