Exam 1 Flashcards

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1
Q

Write the electron configuration for Fe3+ (the atomic # for Fe is 26)

A

Fe3+ has 23 e-

1s2 2s2 2p6 3s2 3p6 3d3 4s2 (would accept 3d5)

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2
Q

Define electronegativity

A

a measure of how strongly atoms attract bonding electrons to themselves
measures how tightly e- are bound to an atom

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3
Q

What is the nearest neighbor direction in FCC crystals? BCC crystals?

A

FCC: <110>
BCC: <111>

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4
Q

What are the 3 types of primary bonds discussed in this class?

A

Metallic
Ionic
Covalent

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5
Q

What are 2 examples of 0-dimensional (point) defects in crystals?

A

Vacancies
Frankel
Schottky
Substitutional

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6
Q

What are the 2 types of 1-dimensional (linear) defects in crystals?

A

Edge
Screw
(With perpendicular symbol before each)

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7
Q

What is one type of 2-dimensional (planar) defects in crystals?

A

Grain boundary

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8
Q

What is a Schottky defect?

A

Both cation and anion missing from an ionic structure. 2 vacancies

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9
Q

What is a Frankel defect?

A

2 cations occupy one lattice site. 1 vaccancy

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10
Q

What is a dipole?

A

A pair of equal and oppositely charged or magnetized poles separated by a distance. Associated with secondary bonding

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11
Q

Why are H bonds so much stronger than Van der Waals forces?

A

H only has one e-. when it gets pulled to one side, it leaves onyl the + nucleus exposed

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12
Q

What is the coordintation number for the BCC crystal structure? For the FCC structure?

A

BCC: 8
FCC: 12

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13
Q

What are hybrid orbitals? Give one example

A

sp orbitals combine to form a new bond geometry

sp2: sp3 orbitals in graphite, diamond

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14
Q

Define covalent bonding, when does it occur?

A

Adjacent atoms share electrons: occurs when electronegativities are equal to each other

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15
Q

Define metallic bonding

A

Lattice of + ion cores surrounded by a sea of e-

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16
Q

What is a side group?

A

Atom or molecule attached to the carbon backbone of a polymer chain.

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17
Q

What is the difference between thermosets and thermoplastics?

A

Thermoplastics can be heated: reformed. Thermo sets will char before flowing.

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18
Q

Write the electron configuration for calcium (Ca, atomic # = 20)

A

1s2 2s2 2p6 3s2 3p6 3d2

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19
Q

Define a thermoset polymer

A
  • A polymer that will burn/char before reforming/melting when heated.
  • A polymer with primary bonds along the chains and between adjacent chains
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20
Q

Van der Waals bonds involve what type of atoms or molecules?

A

dipoles

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21
Q

Two atoms with similar electronegativities will form what type of bond?

A

covalent

22
Q

What are the 4 Hume-Rothery conditions that must be satisfied for complete miscibility of one atom in another

A
  1. Same valence
  2. Same crystal structure
  3. Similar atomic size
  4. Similar electronegativities
23
Q

What are 3 types of point defects?

A

vacancy, interstitial, substitution, Schottky, Frenkel

24
Q

T/F: Violation of one or more Hume-Rothery conditions means that two elements are completely soluble in one another

A

False

25
Q

Define tacticity

A

Tacticity is the pattern of the side groups, following in attaching to a polymer chain: one-sided (isotactic), random (atactic), alternating (syndiotactic)

26
Q

What is a grain? What is a grain boundary?

A

Grain- region of crystalline material in which the orientation of the unit cell is constant

Grain boundary- region of crystalline material where two grains connect.

27
Q

What is the Burgers vector?

A

It defines a unit of motion of a dislocation line

28
Q

What are the 2 types of dislocations discussed in class?

A

Screw and edge

29
Q

Define a crystalline metal

A

A crystalline material possesses long-range order

30
Q

The vertical columns of atoms on the periodic table are referred to as

A

groups

31
Q

The state of each electron orbiting an atom is defined by ______ quantum numbers

A

4

32
Q

Why are the values of atomic mass for each element on the periodic table not whole numbers?

A

The are weighted averages of all isotopes of the material

33
Q

Consider the PE (bond energy) between 2 adjacent atoms. What is the relationship between the force felt by the atoms and the bond energy? What is the value of the force at the equilibrium spacing?

A

F=(dE/da)

When the atoms reach equilibrium spacing (a_o) F=0

34
Q

Write the electron configuration for calcium (Ti2+, atomic # = 22)

A

1s2 2s2 2p6 3s2 3p6

35
Q

Two atoms with very DIFFERENT electronegativities will form what type of bonds?

A

Ionic

36
Q

What are 2 types of line defects?

A

1D: edge, screw

(perpendicular symbol) dislocations

37
Q

T/F: Violation of one or more Humer-Rothery conditions means that 2 elecments are completely insoluble in one another

A

False

38
Q

What are the 3 types of polymer tacticity?

A

isotactic (1 side)
atactic (random)
syndiotactic (alterating)

39
Q

In what type of materials do Schottky defects occur?

A

Ceramics

40
Q

What is a Frenkel defect? In what materials does it occur?

A

2 cations occupy 1 lattice side, 1 vacancy

Ceramics

41
Q

What is the Pauli Exclusion Principle?

A

the quantum mechanical principle which states that two or more identical fermions (particles with half-integer spin) cannot occupy the same quantum state within a quantum system simultaneously

42
Q

The principal quantum number defines the _____ of an orbital

A

size

43
Q

The second quantum number defines the _____ of an orbital

A

shape

44
Q

How many crystal systems are there?

A

7

45
Q

Number of Bravais Lattices are

A

14

46
Q

Length of unit cell edges and angle between crystallographic axes are reffered to as

A

lattice constants

47
Q

Atomic packing factor for FCC is

A

.74

48
Q

Ionic packing factor or MgO is

A

.627

49
Q

What are miller indices?

A

Miller indices give position to lattice planes

50
Q

Define equilibrium bond length a_o? What is the magnitude of the resultant of Columbic attractive and repulsive force at the bond length?

A

Equlilbrium bond length occurs when the attractive force is equal to the repulsive force Fc = Fr

Fc + Fr = 0

51
Q

What is co-ordination number?

A

the # of adjacent ions or atoms surrounding a reference ion or atom