u3: structure and properties of solids

Question 1

physical properties of a solid depend on

Answer 1

• component elements
• attractive forces present (IMFs)

Question 2

types of solids

Answer 2

• ionic solid
• metallic solid
• molecular solid
• covalent network

Question 3

ionic solid definition

Answer 3

• metal and nonmetal
• pos nd neg ion attracted w electrostatic forces

Question 4

metallic solid definition

Answer 4

• two metals
• atoms

Question 5

molecular solid

Answer 5

• two nonmetals
• atoms or molecules

Question 6

covalent network

Answer 6

• metalloids (B, Si, Ge, As, Sb, Te, Po)/carbon
• atoms connected by covalent bonds

Question 7

ionic crystals

Answer 7

• pure ionic compounds in solid form are 3D crystals
• anions nd cations attracted tgthr in crystal lattice
• each anion surrounded by cations nd vice-versa

Question 8

crystal lattice

Answer 8

• regular repeating pattern of ions or molecules in a crystal
• exists in 3 dimensions
• ionic substance held by strong electrostatic attraction in all directions
• directional bonds

Question 9

physical properties of ionic compounds

Answer 9

• hard, brittle, crystalline solids
• high melting and boiling pt (high IMFs)
• don’t conduct electricity as solid, only when molten/aqueous
• soluble in water

Question 10

metallic crystals

Answer 10

• closely packed lattice
• low ionization energies + low energy unfilled orbitals
• valence elecrons become delocalized (shared by all atoms)
• “electron sea model” bc electrons free to move

Question 11

metallic bonding

Answer 11

• atoms lose valence electrons = cations
• cations attracted to free electrons = glue

Question 12

ductility and malleability of metals? alloys?

Answer 12

• attrn not between cations, but cations and mobile electrons: so ions can slide past each other w/o breaking bonds = ductile+malleable
• alloys: pure metal mixed w/ diff metals = harder to slide = harder than pure metals

Question 13

conducting properties of metals

Answer 13

• bc delocalized electrons free to move = good heat nd electricity conductors

Question 14

wht does metal bond strength depend on?

Answer 14

• number of electrons atoms share: more electrons = more hold
• how far from nucleus sea of electrons is

Question 15

how can u figure out melting point based on periodic table

Answer 15

going down a group = lower melting point

Question 16

why are metals shiny?

Answer 16

when electron absorbs light, jumps to excited state. in sea of electrons, its easier to absorb light, so they shine the light back from all wavelengths of visible light

Question 17

molecular crystals

Answer 17

• covalent bonds = molecule
• intra (covalent) stronger than inter

Question 18

physical properties of molecular crystals

Answer 18

• soft in solid state
• dont conduct electricity
• more soluble in non-polar solvent than water
• low melting/boiling pts

Question 19

examples of covalent network solids

Answer 19

• diamonds
• most gemstones

Question 20

physical properties of covalent network solids

Answer 20

• very hard
• brittle (no bending, but v hard so rarely break)
• very high melting points
• insoluble in water
• nonconductors

Question 21

allotropes

Answer 21

diff structural forms of an element

Question 22

allotropes of carbon

Answer 22

• (a) diamond
• (b) graphite
• (d) fullerenes

Question 23

structure of diamond

Answer 23

• each carbon joined to 4 others in tetrahedral shape = very strong structure
• all intramolecular bonds = high melting/boililng pt and hardness

Question 24

structure of graphite

Answer 24

• 2 dimensions covalent network
• made of layers: C atoms bonded to 3 others in trigonal planar form
• each layer is strong
• between layers, there r weak Van der Waals forces

Question 25

does graphite conduct electricity

Answer 25

- yes bc electrons within are free to move from end to end - 3 e are bound, 1 is free to travel

Question 26

how is graphite useful

Answer 26

- large distance between sheets + weak IMFs = layers slide over easily (used as lubricant + pencils)

Question 27

fullerenes

Answer 27

- approx. spherical molecule - small amnt of delocalized electrons, not enough to strongly conduct energy - *behaves electron deficient = readily accepts molecules* - molecular molecule = can dissolve in some non-polar solvents - *lower melting pt than diamond/graphite*

Question 28

silicon

Answer 28

- forms 4 covalent bonds - almost similar structure to diamond

Question 29

silicon dioxide, its structures

Answer 29

- SiO2 - glass, sand, nd quartz r both SiO2 but differ in structure - quartz: crystalline bc. order - glass is not crystalline

Question 30

how is silicon dioxide similar to silicon and diamond

Answer 30

there is an Si with O between all atoms

Question 31

semiconductors

Answer 31

- made of pure silicon/germanium - doped w/ other elements to modify electrical properties - highest energy lvls r full, but w little energy (heat/light) = electron can jump to next level nd begin to travel

Question 32

why do covalent network crystals not conduct electricity

Answer 32

bc in covalent bonds, electrons and held = not mobile