u3: structure and properties of solids Flashcards

1
Q

physical properties of a solid depend on

A
  • component elements
  • attractive forces present (IMFs)
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2
Q

types of solids

A
  • ionic solid
  • metallic solid
  • molecular solid
  • covalent network
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3
Q

ionic solid definition

A
  • metal and nonmetal
  • pos nd neg ion attracted w electrostatic forces
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4
Q

metallic solid definition

A
  • two metals
  • atoms
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5
Q

molecular solid

A
  • two nonmetals
  • atoms or molecules
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6
Q

covalent network

A
  • metalloids (B, Si, Ge, As, Sb, Te, Po)/carbon
  • atoms connected by covalent bonds
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7
Q

ionic crystals

A
  • 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
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8
Q

crystal lattice

A
  • 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
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9
Q

physical properties of ionic compounds

A
  • hard, brittle, crystalline solids
  • high melting and boiling pt (high IMFs)
  • don’t conduct electricity as solid, only when molten/aqueous
  • soluble in water
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10
Q

metallic crystals

A
  • 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
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11
Q

metallic bonding

A
  • atoms lose valence electrons = cations
  • cations attracted to free electrons = glue
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12
Q

ductility and malleability of metals? alloys?

A
  • 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
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13
Q

conducting properties of metals

A
  • bc delocalized electrons free to move = good heat nd electricity conductors
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14
Q

wht does metal bond strength depend on?

A
  • number of electrons atoms share: more electrons = more hold
  • how far from nucleus sea of electrons is
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15
Q

how can u figure out melting point based on periodic table

A

going down a group = lower melting point

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16
Q

why are metals shiny?

A

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

17
Q

molecular crystals

A
  • covalent bonds = molecule
  • intra (covalent) stronger than inter
18
Q

physical properties of molecular crystals

A
  • soft in solid state
  • dont conduct electricity
  • more soluble in non-polar solvent than water
  • low melting/boiling pts
19
Q

examples of covalent network solids

A
  • diamonds
  • most gemstones
20
Q

physical properties of covalent network solids

A
  • very hard
  • brittle (no bending, but v hard so rarely break)
  • very high melting points
  • insoluble in water
  • nonconductors
21
Q

allotropes

A

diff structural forms of an element

22
Q

allotropes of carbon

A
  • (a) diamond
  • (b) graphite
  • (d) fullerenes
23
Q

structure of diamond

A
  • each carbon joined to 4 others in tetrahedral shape = very strong structure
  • all intramolecular bonds = high melting/boililng pt and hardness
24
Q

structure of graphite

A
  • 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
25
Q

does graphite conduct electricity

A
  • yes bc electrons within are free to move from end to end
  • 3 e are bound, 1 is free to travel
26
Q

how is graphite useful

A
  • large distance between sheets + weak IMFs = layers slide over easily (used as lubricant + pencils)
27
Q

fullerenes

A
  • 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
28
Q

silicon

A
  • forms 4 covalent bonds
  • almost similar structure to diamond
29
Q

silicon dioxide, its structures

A
  • SiO2
  • glass, sand, nd quartz r both SiO2 but differ in structure
  • quartz: crystalline bc. order
  • glass is not crystalline
30
Q

how is silicon dioxide similar to silicon and diamond

A

there is an Si with O between all atoms

31
Q

semiconductors

A
  • 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
32
Q

why do covalent network crystals not conduct electricity

A

bc in covalent bonds, electrons and held = not mobile