CaF2; ionic solid; metallic solid

Question 1

what is the cation: anion ratio of CaF2

Answer 1

1:2

Question 2

true or false; the fcc array of Ca(2+) ions with F(-) ions occupy all tetrahedral sites

Answer 2

true

Question 3

what is the formula for the general structure of salts; with generally large cations and generally small anions

Answer 3

MX2

Question 4

how many Ca(2+) ions in CaF2

Answer 4

4

Question 5

how many F(-) ions in CaF2

Answer 5

8

Question 6

true or false; the ions sitting at the holes of the lattice (fcc or cubic) are bigger than the holes themselves

Answer 6

true

Question 7

what is the effect, when the ions are bigger than the holes

Answer 7

this causes the expanding of the lattice and reducing contacts between ions of like charge

Question 8

true or false; when the size of the hole decreases, the size of the ions surrounding the hole decreases

Answer 8

true

Question 9

what is the radius of a sphere that fits the tetrahedral hole

Answer 9

0.2

Question 10

what is the radius of the sphere that fits the octahedral hole

Answer 10

0.4

Question 11

what is the radius of a sphere that fits the cubic hole

Answer 11

0.7

Question 12

In ionic solids what causes the high lattice energy?

Answer 12

the fixed ion positions are bonded to each other with very strong interionic (electrostatic) forces

Question 13

is the mp of an ionic solid high or low?

Answer 13

high

Question 14

why do ionic solids have low electrical conductivity in the solid state?

Answer 14

the ions are not free to move thus they cannot conduct electrical charge

Question 15

why are ionic solids hard?

Answer 15

because only strong external forces can change the relative positions of trillions of interaction ions

Question 16

why does an ionic solid crystal crack

Answer 16

when enough force is applied to move them, like ions are brought close together and their repulsions crack the crystal

Question 17

when a force is applied to a metallic solid, what happens?

Answer 17

• metals bend

- metals are deformed

Question 18

true or false; metals are able to conduct heat and electricity in both solid and liquid states?

Answer 18

true

Question 19

what STRONG forces hold metal atoms together

Answer 19

metallic bonding forces

Question 20

how does the strong metallic bonding forces influence the mp and bp of a metallic solid

Answer 20

they are both high

Question 21

what is the simplistic way of viewing the bonding in metals?

Answer 21

all metals in a sample contribute their valence electrons to form an “electron sea” that is DELOCALIZED throughout the sample

Question 22

true or false; the metal atoms (minus their valence electrons) form a regular array WITHIN this “sea” of electrons

Answer 22

true

Question 23

true or false; no metals atoms are bonded through a localized pair of electrons

Answer 23

true

Question 24

meaning of localized electrons

Answer 24

electrons that are not in the valence band or conduction band; rather in the inner shell electrons

Question 25

meaning of delocalized electrons

Answer 25

electrons shared among the crystal or molecule and will form part of the energy band

Question 26

what properties of metals do the electron sea model account for

Answer 26

• regularity (but not rigidity) of metal atom array

- mobility & delocalized nature of valence electrons

Question 27

what happens when force is applied to a metallic solid?

Answer 27

the metal ions slide past each other through the electron sea to new lattice positions

Question 28

why are metals good conductors of electricity?

Answer 28

because they have mobile electrons

Question 29

why are metals good conductors of heat

Answer 29

because of their mobile electrons

Question 30

what does the molecular orbital band theory describe

Answer 30

the bonding in metals, metalloids, non metals