Module 4: Exam 3

Question 1

Number of atoms in the unit cell of a simple cubic cell

Answer 1

1

Question 2

Number of atoms in the unit cell of a body centered cubic

Answer 2

2

Question 3

Number of atoms in the unit cell of a face centered cubic

Answer 3

4

Question 4

What fraction of a cell is on the corner of a unit cell?

Answer 4

1/8

Question 5

What fraction of a cell is on the edge of a unit cell?

Answer 5

1/4

Question 6

What fraction of a cell is on the side of a unit cell?

Answer 6

1/2

Question 7

Packing efficency of simple cubic

Answer 7

52%

Question 8

Packing efficiency of body centered cubic

Answer 8

68%

Question 9

Packing efficiency of face centered cubic

Answer 9

74%

Question 10

What is a coordination number?

Answer 10

The number of other atoms that are touching a particular atom

Question 11

Coordination number of simple cubic

Answer 11

6

Question 12

Coordination number of body centered cubic

Answer 12

8

Question 13

Coordination number of face centered cubic

Answer 13

12

Question 14

Edge length formula of simple cubic

Answer 14

2r

Question 15

Edge length formula of face centered cubic

Answer 15

2(sqrt 2) * r

Question 16

Edge length formula of body centered cubic

Answer 16

4/(sqrt3) *r

Question 17

Which cubic model has the least amount of space between the atoms?

Answer 17

Face centered cubic

Question 18

Crystalline solids

Answer 18

rigidly held in place

Question 19

Amorphous solids

Answer 19

free to move around

Question 20

What type of electrons do metals have?

Answer 20

Electrons that are free to move around

This makes them good conductors of electricity since they can transfer kinetic energy

Question 21

Why are two neutral hydrogen atoms attracted to eachother?

Answer 21

As force of attraction increases, the potential energy decreases

This allows them to move to a state of lower potential energy

Question 22

What happens to two atoms when they get too close together?

Answer 22

There is repulsion between the two nuclei and there is electron-electron repulsion

Question 23

On a potential energy curve for the interaction of two atoms, where is change in potential energy 0?

Answer 23

At the bottom of the “sweet spot” dip

Question 24

On a potential energy curve for the interaction of two atoms, where do repulsive forces overcome the attractive forces?

Answer 24

Once potential energy crosses the x-axis and becomes positive

Question 25

As force of attraction increases, what happens to potential energy?

Answer 25

It decreases Until a certain point where force of repulsion overcomes because two atoms are too close

Question 26

Bond length

Answer 26

the distance(r) that makes change in potential energy 0

Question 27

Would a deeper potential energy well result in a stronger or weaker bond?

Answer 27

Stronger less potential energy (deeper) = greater force of attraction

Question 28

Why does an ionic solid have to be expressed by an empirical formula?

Answer 28

Because it can go on forever Therefore, need to simplify to ratio because there is no exact amount

Question 29

Difference between ionic bond and covalent bond

Answer 29

Ionic bond involves the complete transfer of an electron (metal and nonmetal) Covalent bond involves the sharing of electrons

Question 30

Percent ionic character

Answer 30

how ionic a bond is

Question 31

Why is bonding a continuum?

Answer 31

different differences in electronegativies make some bonds and charges stronger than others?

Question 32

What does electronegativity tell us?

Answer 32

In a polar covalent bond, it will tell us which atom the electron is going to be pulled towards

Question 33

Example of a pure nonpolar covalent

Answer 33

O2 there is no difference in electronegativities

Question 34

Example of an ionic bond

Answer 34

NaCl large difference in electronegativies, complete transfer of electrons

Question 35

Which type of bond is normally the strongest?

Answer 35

Ionic

Question 36

How do you determine the most polar covalent?

Answer 36

The greatest difference in electronegativity

Question 37

How do you determine the most polar covalent?

Answer 37

The greatest difference in electronegativity

Question 38

Percent ionic character of a complete ionic bond

Answer 38

100%

Question 39

Percent ionic character of a complete covalent bond

Answer 39

0%

Question 40

Percent ionic character of Na-Cl

Answer 40

79% *nothing is perfect*

Question 41

Percent ionic character of Na-Cl

Answer 41

79% *nothing is perfect*

Question 42

Is polar or nonpolar covalent a stronger bond?

Answer 42

In general, nonpolar covalent is stronger However, have to take into consideration things like electron-electron repulsion

Question 43

Why is bond length of Cl2 longer than H2?

Answer 43

Cl2 has a larger radius, which makes the length longer also decreases the force of attraction, making the bond between H2 stronger

Question 44

When does the atomic radius argument for bond length NOT work?

Answer 44

Size argument is negligible within the same period

Question 45

Relationship between formal charges and force of attraction

Answer 45

Formal charges increase the force of attraction and strengthen the bond

Question 46

Relationship between lone pairs and force of attraction

Answer 46

Lone pairs weaken the force of attraction and weaken the strength of the bond it also makes the bond longer, since it is weaker

Question 47

What can effect the length of a bond?

Answer 47

If the atoms have the same charge, this increases repulsion and resultingly lowers force of attraction, making a longer bond

Question 48

Is there a greater difference in electronegativity between row or column?

Answer 48

If you move up a column and 2 over, that is normally a greater difference than moving DIRECTLY up a column

Question 49

Coordination number of ions that are wedged between face centered? Only on edges?

Answer 49

6