Network covalent solids Flashcards
true or false; in a crystalline solid, separate particles are not present
true
how are the atoms linked together in a crystalline solid
strong covalent bonds link the atoms together throughout a network covalent solid
What does conductivity and hardness of a crystalline solid depend on?
depends on details of bonding
why is diamond non conducting and hard
it has localized covalent bonding
why is graphite soft and conducts electricity
has delocalized electrons
what are the most important network solids?
silicates
what do most silicates consist of?
covalently bonded Si-O
What is the color of graphite?
black and shiny
what is the color of diamond
colorless, transparent
What are amorphous solids?
non crystalline
-sometimes they have small ordered regions connected by large disordered regions
what are examples of amorphous solids?
glass, rubber and charcoal
what is SiO2
crystalline quartz, cubic closest packed structure
what happens when SiO2 is melted then the viscous liquid is cooled rapidly?
recrystallization is prevented
the disordered chains cannot orient themselves quickly enough to form crystalline solid
what happens when the recrystallization of SiO2 is prevented by rapid cooling after melting?
they solidify in a disordered jumble containing many gaps and misaligned rows called a GLASS
what are glass sometimes called?
super cooled liquids
absence of structural regularity
What are the essential components of ceramic materials?
- defined as synthetic materials
- main components are: inorganic, nonmetallic materials
How much in % does oxygen and silicon together make up the mass of the earth’s crust?
75%
describe the Si-O bond?
- strong’
- partially ionic
What class is Si-O a basis of?
class of silicates
true or false; silicates make up the bulk of rocks, clays , sand and soils in the earth’s crust
true
true or false; silicates provide the ingredients for building materials such as bricks, cement and glass
true
what tetrahedral group is the basic unit upon which all the silicates are based?
SiO4
the minerals in the silicates group has which common anion?
SiO4 (-4)
what do the complex units of silicates share with each other?
one or more oxygen atoms between tetrahedral units
true or false; in silicate structures, bridging O atoms do not contribute to the overall charge of the anion
true
what oxygen atoms of silicates contribute to the overall charge of the anion?
terminal O atoms contribute a -1 charge to the anion
