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CHEM1B > Week 6 Solids > Flashcards

Week 6 Solids Flashcards

1
Q

Constructive and Destructure Interference
What is Braggs law

A

Constructive: when 2 waves with crests and troughs perfectly align (2x amplitude)
Destructive: When two waves with crests that alighn with troughs (0 amplitude)
d=nlanda/2sintheta
d=distance, n is positive integer in moles, theta is angle of incidence, landa is wavelenth

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2
Q

Unit Cell

A

A collection of atoms, ions, molecules that is repeating unit of a crystalline lattice

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3
Q

Crystalline lattice

A

A repitition of the unit cell

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4
Q

Simple Cubic

How many atoms per unit cell, CN, edge length formula, packing eff.

A

1 Atom, 6 CN, l=2r, 52%

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5
Q

body Centered cubic cell
How many atoms per unit cell, CN, edge length formula, packing eff.

A

2 Atoms/unit cell, 8 CN, l=4r/sqrt3, 68%

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6
Q

Face centered cubic cell

A

4 Atoms, 12 CN, 2(sqrt2)r, 74%

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7
Q

How many atom/unit cell is in each of the following:
Corner
Edge
Face
Body

A

Corner=1/8
Edge=1/4
Face=1/2
Body:1

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8
Q

How do you get the unit cells for Simple, BCC, FCC

A

Simple=(1/8)(8)
BCC= 1+ (1/8)(8)
FCC=(1/8)(8) + (1/2)(6)

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9
Q

What are the 2 types of stacking - which is more efficient

A

Direct row
Half sphere offset row- more efficient

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10
Q

How do you get a tetrahedral structure

A

Offset layer stacking of Layers B on Layer A (in between the layers)

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11
Q

What are the closest packed styuctures called, what are their packing efficiency, how are they layered

Wh ich one is FCC

A

Both have 74%
Hexagonal:ABA
Cubic: ABC

Cubic is FCC

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12
Q

What is the formula to get packing efficiency

A

(N Atom)(V atom)/V Unit cell

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13
Q

What is the degree of order for Solids

A

Amorphous-Short range
Polycrystalline-Mid range
Crystalline- long range

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14
Q

What are the crystalline solids

A

Molecular solids- molecules- low melting points
Ionic solids- Have cations and anions-high meling points

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15
Q

Atomic solids (units are atoms)

A

Nonbonding-dispersion forces- low melting pt (mainly noble gases)
Metallic- metallic bonds- variable melting pts
Network Covalent- held together by covalent bonds- high melting pt

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16
Q

Molecular solids
What are the composite units, melting pt, what are they held by, conduction, what are some examples

A
  1. Composite units are molecules
  2. Low melting pt
  3. Held together by IMF
  4. Poor conductures of heat/electricity
  5. Ice, Dry ice, iodine MOLECULES
17
Q

What are molecular solids with different crystalline stuctures called

A

Polymorphs- Different polymorphs of ice is why there are different patterns of snowflakes

18
Q

Ionic Solids
Composite units, where do larger/smaller ion occupy, melting pt, conduction, examples

A
  1. Composite units are formula units (cations and anions)
  2. Larger ions occupy lattice/smaller occupy holes in unit cell (Na+ in holes, Cl- in lattice)
  3. High melting pts, held together by strong ionic bonds
  4. Poor conductors in solid, good conductors in aqueous state
  5. Brittle
  6. CsCl, NaCl
19
Q

Nonbonding
Composite units, held together by, which group, melting pt, conduction

A
  1. Composite units are individual atoms
  2. Held together by dispersion
  3. Group 8
  4. Low melting pts, increase with molar mass
  5. Poor conductors of heat amd electricity
20
Q

Metallic
Composite units, melting pt, conduction, what are some cool properties

A
  1. Composite units are individual atoms (metal cations in lattice position)
  2. High melting pt
  3. Good conductors of heat and electricity in solid state
  4. Malleable- hammered into thin sheets
  5. Ductile- wires
  6. Layers of cations can slide over each other
21
Q

Network covalent
Composite units, melting pt, conduction, how are they held

A
  1. Composite units are individual atoms
  2. Formed by non mentals such as (C,Si,As and its oxides or carbides)
  3. VERY high melting pts
  4. Atoms at lattice pts held together by strong covalent bonds
  5. Poor conductors of heat and electricity (BESIDES graphite)
22
Q

What are the allotropes of Carbon

A

Different forms of network covalent atomic solids of elemental carbon called allotropes
Graphite: 3 valence e= for bonding,1 valence electron free to travel, weak dispersion forces
Diamind: very hard, extensive nework of covalent bonds, each C bonded to 4 other C in a tetrahedral

CHEM1B (12 decks)

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