Test 1: Ch 1-3

Question 1

Scope of MSE

Answer 1

chemistry, physics, engineering

Question 2

Metals

Answer 2

• atoms are located in repeating positions (crystal)
• free electrons making metals good conductors
• strong but dense
• moderate temp resistance
• ductile

Question 3

Ceramics

Answer 3

• metallic and non-metallic atoms
• many, but not all, are crystalline
• no free electrons
• very strong, moderate density, high temp stability
• brittle

Question 4

Polymers

Answer 4

• long chain molecules with repeating groups
• low strength, temp sensitive
• easy to form into complex shapes
• low density, ductile or brittle
• covalently bonded

Question 5

Semiconductors

Answer 5

• bonding similar to ceramics, require high purity
• mechanical properties similar to ceramics
• covalently bonded

Question 6

Composites

Answer 6

• two or more materials combined

- structural applications where rigidity strength and low density are critical

Question 7

Atomic Scale

Answer 7

pm

Question 8

Unit Cell Scale

Answer 8

sub nm

Question 9

Grain size scale

Answer 9

nm, µm

Question 10

Life size scale

Answer 10

nm, µm, mm, m, km

Question 11

Primary atomic bonding

Answer 11

ionic, covalent, metallic

Question 12

Secondary atomic bonding

Answer 12

Van der Waals, Hydrogen

-arises from interaction b/w dipoles

Question 13

ionic bonding

Answer 13

• charge transfer
• from the extremes of the periodic table, large difference in electronegativity
• metals and nonmetals
• transfer of an electron from the electropositive atom to the electronegative atom

Question 14

covalent bonding

Answer 14

-sharing electrons in an attempt to make a complete shell

Question 15

metallic bonding

Answer 15

-electrons shared by all the atoms in the substance

Question 16

Force curves

Answer 16

-the steeper the slope of a force curve at the equilibrium distance, the higher the elasticity

Question 17

Characteristics of Ionic Bonding

Answer 17

• bonding energy 150-370 Kcal/mol
• non-directional bond (strength of bond equal in all directions)
• low electrical conductivity
• brittle and high melting temp

Question 18

Coordination number and Geometry

Answer 18

2-linear
3-triangular
4-tetrahedral, square planar

Question 19

coordination number

Answer 19

how many atoms are in contact with another

Question 20

Characteristics of covalent bonding

Answer 20

• electrons are shared to form a bond
• bonding energy is less than ionic (75-300)
• directional bonding (bond not of equal strength in all directions

Question 21

covalent crystalline solids

Answer 21

• high melting temperatures
• low conductivity
• very hard and brittle

Question 22

Characteristics of metallic bonding

Answer 22

• electrons are shared to form a bond
• medium strength bonds
• bonding energy weakest (25-200)
• non-directional bond (strength of bond equal in all directions)
• conductors
• ductile

Question 23

Van der Waals bonding

Answer 23

• weak bonding

- often bonding force between molecules

Question 24

Hydrogen bonding

Answer 24

-special type of secondary bond between some molecules containing Hydrogen (Cl, N, O, F)

Question 25

Bravais Lattices (4)

Answer 25

- cubic - tetragonal - orthorhombic - rhombahedral

Question 26

Types of cubic crystal structures

Answer 26

- face centered cubic - body centered cubic - simple cubic

Question 27

FCC

Answer 27

- face centered cubic - 4 lattice points ((1/8 x 8)+ 1/2 x 6) - CN = 12 - APF = 4r/sqrt(2)=.740

Question 28

BCC

Answer 28

- body centered cubic - 2 lattice points - CN = 8 - APF = 4r/sqrt(3) = .680

Question 29

SC

Answer 29

- simple cubic - 1 lattice point - CN = 6 - APF = .52

Question 30

Atomic Packing Factor (APF)

Answer 30

volume of atoms in unit cell/ volume of unit cell

Question 31

ceramic bonding

Answer 31

mostly ionic, some covalent | -ionic character increases with difference in electronegativity

Question 32

polymorphism

Answer 32

the same atoms can have more than one crystal structure

Question 33

FCC stacking sequence

Answer 33

ABCABC...

Question 34

BCC stacking sequence

Answer 34

ABABAB...

Question 35

alloys

Answer 35

atomic-sale mixtures of atoms

Question 36

electropositive

Answer 36

gives up an electron more easily than gaining one (3 or less valence electrons)

Question 37

electronegative

Answer 37

gains an electron more easily than it loses one (5 or more valence electrons)

Question 38

When is a bond half ionic and half covalent?

Answer 38

when the difference of electronegativity is 1.7 | -when lower, more covalent. when higher, more ionic

Question 39

Long range order (LRO)

Answer 39

Materials that exhibit order over distances much greater than the bond length

Question 40

Short range order

Answer 40

the local arrangement of nearest-neighbor atoms about a central atom

Question 41

Lattice Points

Answer 41

the vertices of the unit cell

Question 42

Lattice Parameter

Answer 42

the length of the unit cell edges