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inorganic chem > 2: Solid state Chem > Flashcards

2: Solid state Chem Flashcards

Topic 2

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1
Q

Crystalline solids

A

atoms, ions or molecules of the material are arranged in a definite repeating pattern
The repeating patterns are fundamental properties and influence macroscopic behaviour
Metals, ions and small molecules typically for crystals

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2
Q

Amorphous solids

A

form when liquids freeze before the molecules can arrange into an orderly pattern
Lack ordered internal structure
Glasses
Non-crystalline materials
Large molecules or mixtures with restricted movement often form amorphous solids

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3
Q

Molecules that can form both amorphous and crystalline solids

A

Silicon dioxide can crystallise in several crystalline forms (quartz)
Rapid cooling forms amorphous fused silica

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4
Q

Types of crystalline solids

A

Ionic, metallic, covalent network, molecular

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5
Q

Ionic solids

A

made up of ions
positive and negatively charged ions
hard but brittle and shatter
high lattice energies
high m.p.
not conductive when solid
conductive when molten

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6
Q

Ionic solids

A

made up of ions
positive and negatively charged ions
hard but brittle and shatter
high lattice energies
high m.p.
not conductive when solid
conductive when molten
NaCl

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7
Q

Metallic solids

A

Atomic nuclei in a sea of delocalised electrons
metallic bonding
hard, malleable, don’t shatter
high thermal and electric conductivity
variable melting points
Copper

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8
Q

Covalent network solids

A

3D network of covalent bonds
non-metals
strong covalent bonds
very high m.p
Diamond

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9
Q

Molecular solids

A

neutral molecules held together by intermolecular forces
M.p varies based on intermolecular forces
small symmetrical non-polar molecules have weak attractive forces low m.p
molecules with permanent dipole higher m.p
H2O

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10
Q

Types of cubic unit cell

A

simple, face-centred, body-centred

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11
Q

Simple cubic unit cell

A
  • Particles at 8 corners
  • No central particle
  • Spheres touch
  • Not packed efficiently
  • 48% empty
  • Metallic polonium = only known example
  • Each atom touching 6 others
  • Coordination no. = 6
  • PPUC = 8 x (1/8) = 1
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12
Q

Density of unit cell

A

Find number of particles in unit cell
PPUC
D = M/V
V = 2r^3
Find mass per particle
Molar mass/6 x 10^23 = mass per particle
D = M/V

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13
Q

Body-centred cubic unit cell

A
  • Particles at all 8 corners
  • 1 particle in the centre
  • Centre particle touches all corners
  • More efficiently packed than simple cubic
  • 32% empty space
  • Common structure for metals
  • Lithium
  • CN = 8. central atom touching 8 corner
  • PPUC = (1)(1) + (8)(1/8) = 2
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14
Q

Face-centred cubic

A
  • Particles at all 8 corners
  • Particles at the centre of all 6 faces
  • No central particle
  • Corner spheres touch face spheres but not other corners
  • Very efficiently packed
  • 26% empty space
  • Common for metals
  • Al, Ca, Ni
  • Copper
  • CN = 12
  • PPUC = (6)(1/2) + (8)(1/8) = 4
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15
Q

Copper as an antimicrobial surface

A
  • copper shows contact killing effect
  • copper surfaces kill pathogens
  • likely due to release of ions leads to radical oxygen species that damage DNA and membrane
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16
Q

Hexagonal close packing

A

triangular holes
one layer offset from the other
74% packing efficiency
Magnesium

17
Q

Cubic close packing

A

3 layer offset from each other
fcc
74% packing efficiency
Copper

18
Q

Interstitial sites

A
  • Smaller cations fit into holes
  • Not all holes equal shape and size
  • for every n particles there are n octahedral holes and 2n tetrahedral holes
19
Q

Interstitial holes types

A

cubic hole
octahedral holes
tetrahedral holes

20
Q

Cubic hole

A

a particle in this hole would touch 8 other particles

21
Q

Octahedral hole

A

a particle in this hole would touch 6 other particles

22
Q

Tetrahedral hole

A

a particle in this hole would touch 4 other particles

23
Q

Cation and anion of similar size lattice
AB structure

A
  • Caesium chloride (CsCl)
  • Simple cubic lattice
  • large anion fills cubic hole in centre
  • NOT bcc AS ALL PARTICLES NOT IDENTICAL
  • Anion:Cation = 1:1
  • 1 CsCl/cell
24
Q

Cations smaller than anions lattice AB structure

A
  • NaCl
  • FCC Na in octahedral holes
  • 1:1
  • alkali halides
  • alkali hydrides
  • monoxides
  • monosulphides
25
Q

Cation much smaller than anion lattice AB

A
  • Zinc Blende
  • ZnS
  • fcc of sulfide/anion
  • Zn in 50% of tetrahedral holes
  • As charge dictates 1:1 but particles to tetrahedral holes are 1:2, only fill half tetrahedral holes
26
Q

Fluorite structure (CaF2) AB2

A
  • when 1:2 stoichiometry, all tetrahedral holes can be filled in fcc array
  • Cations Ca2+ make up fcc
  • F- fills holes
  • ^ due to Ca:F = 1:2
  • Ca in cubic environment - touch 8
  • F in tetrahedral environment touch 4
27
Q

Anti-fluorite AB2 lattice structure

A
  • anions fill fcc spaces
  • cation fills tetrahedral holes
  • M2O - M = alkali metal
28
Q

Rutile structure (TiO2) AB2 lattice structure

A
  • Ti cations bcc tetragonal lattice
  • Oxides in trigonal holes
  • each Ti is octahedral environment
  • SnO2, ZrO2
29
Q

Rhenium trioxide structure (ReO3) AB3

A
  • Re has simple cubic lattice
  • O in between each Re along edges
  • 1:3
  • lots of unfilled space
30
Q

Perovskite (CaTiO3) ABX3

A
  • Same as ReO3 but with central cavity filled by additional element
  • Ternary oxides ABO3
  • Larger ion in gap
31
Q

Network solids: Cristobalite (SiO2) AB2 network covalent solid

A
  • resembles zinc blende structure
  • fcc lattice of Si
  • 50% tet holes filled by Si
  • O between each Si atom
  • Si CN = 4
  • O CN = 2
  • BeF2 similar structure
32
Q

Most stable C allotrope under standard conditions?

A

Graphite.
stacked sheets of trigonal planar carbon form strong sigma network.
Delocalised pi electrons can conduct electricity
hexagonal solid state structure with ABAB layers.

33
Q

Carbon allotrope under high pressure

A

Diamond
tetrahedrally arranged network
fcc lattice of C
with 50% of tetrahedral holes filled
CN = 4

34
Q

C60

A
  • Buckminsterfullerene
  • not covalent network
  • A molecule of C60 can form solid state structures with others
    fcc unit cell with other C60 molecules
35
Q

Defects in solid state structures

A

vacancies = atom/ion missing
interstitial impurity = atoms or ions fit into gaps
substitution impurity = atom/ion replaces on in the lattice if similar size or will distort if much larger

36
Q

Doping of semiconductors

A

defects may introduce holes/extra valence electrons
may conduct electricity

37
Q

Alloy

A

metal mixture of two or more pure elements
ductile, malleable, good conductors

inorganic chem (4 decks)

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