Network covalent solids

Question 1

true or false; in a crystalline solid, separate particles are not present

Answer 1

true

Question 2

how are the atoms linked together in a crystalline solid

Answer 2

strong covalent bonds link the atoms together throughout a network covalent solid

Question 3

What does conductivity and hardness of a crystalline solid depend on?

Answer 3

depends on details of bonding

Question 4

why is diamond non conducting and hard

Answer 4

it has localized covalent bonding

Question 5

why is graphite soft and conducts electricity

Answer 5

has delocalized electrons

Question 6

what are the most important network solids?

Answer 6

silicates

Question 7

what do most silicates consist of?

Answer 7

covalently bonded Si-O

Question 8

What is the color of graphite?

Answer 8

black and shiny

Question 9

what is the color of diamond

Answer 9

colorless, transparent

Question 10

What are amorphous solids?

Answer 10

non crystalline

-sometimes they have small ordered regions connected by large disordered regions

Question 11

what are examples of amorphous solids?

Answer 11

glass, rubber and charcoal

Question 12

what is SiO2

Answer 12

crystalline quartz, cubic closest packed structure

Question 13

what happens when SiO2 is melted then the viscous liquid is cooled rapidly?

Answer 13

recrystallization is prevented

the disordered chains cannot orient themselves quickly enough to form crystalline solid

Question 14

what happens when the recrystallization of SiO2 is prevented by rapid cooling after melting?

Answer 14

they solidify in a disordered jumble containing many gaps and misaligned rows called a GLASS

Question 15

what are glass sometimes called?

Answer 15

super cooled liquids

absence of structural regularity

Question 16

What are the essential components of ceramic materials?

Answer 16

• defined as synthetic materials

- main components are: inorganic, nonmetallic materials

Question 17

How much in % does oxygen and silicon together make up the mass of the earth’s crust?

Answer 17

75%

Question 18

describe the Si-O bond?

Answer 18

• strong’

- partially ionic

Question 19

What class is Si-O a basis of?

Answer 19

class of silicates

Question 20

true or false; silicates make up the bulk of rocks, clays , sand and soils in the earth’s crust

Answer 20

true

Question 21

true or false; silicates provide the ingredients for building materials such as bricks, cement and glass

Answer 21

true

Question 22

what tetrahedral group is the basic unit upon which all the silicates are based?

Answer 22

SiO4

Question 23

the minerals in the silicates group has which common anion?

Answer 23

SiO4 (-4)

Question 24

what do the complex units of silicates share with each other?

Answer 24

one or more oxygen atoms between tetrahedral units

Question 25

true or false; in silicate structures, bridging O atoms do not contribute to the overall charge of the anion

Answer 25

true

Question 26

what oxygen atoms of silicates contribute to the overall charge of the anion?

Answer 26

terminal O atoms contribute a -1 charge to the anion