Chem Quiz 2

Front 1

crystalline solids

Back 1

highly regular atomic arrangements

Front 2

amorphous solids

Back 2

disordered atomic arrangements

Front 3

lattice

Back 3

a three-dimensional array of points designating the centers of the components (atoms, ions, or molecules) that shows the repetitious pattern of the components

Front 4

unit cell

Back 4

the smalles repeating unit of the lattice

Front 5

X-ray diffraction

Back 5

the scattering of light from a regular array of points or lines. the spacing between the points or lines (planes for atoms) are related to the wavelength of the light. x-rays are used because there wavelengths are similar to distances between the atomic nuclei

Front 6

ionic solids

Back 6

form electrolytes when dissolved in water (NaCl) [brittle, high melting temp]

Front 7

molecular solids

Back 7

do not form electrolytes when dissolved (H20 - ice) [strong forces within molecules and weak inter molecular forces between molecules]

Front 8

atomic solid

Back 8

contains atoms of only one element, which are covalently bonded together (Diamond)

Front 9

Bragg Equation

Back 9

n(wavelength) = 2d sin (angle), where d is the distance between the atoms and angle is angle of incidence and reflection

Front 10

protein crystallography

Back 10

if a protein can be turned into a crystal then its structure can bet studied this way.

Front 11

constructive interference

Back 11

when waves are in phase (peaks on top of each other), the addition of these two waves has an amplitude equal to the sum of each

Front 12

destructive interference

Back 12

when waves are not in phase, the sum of the waves equals zero

Front 13

closest (or close) packed

Back 13

spheres packed as efficiently together as possible

Front 14

hexagonal closest packed (hcp) structure

Back 14

the resulting structure formed by an aba arrangement, with a hexagonal unit cell
(coordination number is 12)

Front 15

cubic closest packed (ccp) structure

Back 15

the resulting structure formed by an abc arrangement, with a face-centered cubic unit cell (coordination number is 12)

Front 16

body centered cubic structure

Back 16

spheres are not closest packed, (coordination number is 8, 2 spheres per unit cell [1 full + 8 1/8)

Front 17

simple cubic

Back 17

formed by packing spheres on top of each other, not closest packed (each unit cell contains 8 1/8 spheres, = 1 total sphere, coordination number =8)

Front 18

band model

Back 18

molecular orbital model for metals, electrons are assumed to travel around the metal crystal in MOs formed from the valence atomic orbitals of the metal atoms

Front 19

holes

Back 19

spaces left by the packing of atoms that define the unit cell [trigonal < tetrahedral < octahedral < cubic)

Front 20

substitutional alloy

Back 20

some of the host metal atoms are replaced by the other metal atoms of a similar size (ex. brass)

Front 21

interstitial alloy

Back 21

formed when some of the holes in the closest packed metal structure are occupied by small atoms

Front 22

CO2 vs SiO2

Back 22

CO2 forms one sigma bond a one pi bond with oxygen

SiO2 (silica), however due to the large size of 3p orbitals, cannot form good pi bonds, so it froms networks build from single bonds

Front 23

silica

Back 23

SiO2, where each O is shared between two Si

ex. quartz

Front 24

silicates

Back 24

have O-Si ratios greater than 2:1 and thus some O are not fully bonded to the ions

ex. Feldspar, and many minerals

Front 25

N-type semiconductors

Back 25

formed by adding small amounts of atoms with extra valence electrons, allowing for easier movement of conductions

Front 26

P-type semiconductors

Back 26

formed by adding a small amount of an element that has less valence electrons than silicon, forming positively charged holes that become occupied by electrons from neighboring atoms

Front 27

mass percent

Back 27

grams solute/ total grams (solute + solvent) = (grams/grams) x 100%

Front 28

molarity

Back 28

moles solute / volume of solution = M = (mol/L)

Front 29

p-n junction

Back 29

a small number of electrons migrate from the N-type region to the P-type region, where there are vacancies in the lower MOs.

Front 30

critical temperature

Back 30

the temperature above which the vapor cannot be liquified no matter how much pressure is applied