question

tetrahedral void

answer

0.225r

question

octahedral void

answer

0.414r

question

cubic void

answer

0.732r

question

Polymorphism

answer

The ability to adopt different crystal forms under different conditions of pressure and temperature

question

Alloy

answer

Blend of metallic elements prepared by mixing molten components and then cooling to produce a solid

question

Interstitial solid solutions

answer

Formed between metals and small atoms that can occupy voids while maintaining crystal structure

question

Rock salt structure

answer

Ccp array of bulky anions with cations in all octahedral holes with 6:6 coordination

question

Cesium chloride structure

answer

Primitive cubic unit cell with each corner occupied by an anion and a cation occupying cubic hole at the center ; z=1

question

Sphalerite/Zinc Blende

answer

Expanded ccp anion arrangement but actions occupy one type of td hole (1/2 holes present) 4:4 coordination, Z =4

question

Wurtzite/Zinc Blende

answer

Derived from sphalerite but dorms expanded hcparray

question

ZnS type 1

answer

zinc blende; FCC lattice arrangement (Ccp)

question

ZnS type 2

answer

wurtzite; has an hcp packing lattice

question

For a radius ratio of 1: What is the coordination number? Binary AB type structure? Binary AB2 structure?

answer

12; none known, none known

question

For a radius ratio of 0.732 to 1: What is the coordination number? Binary AB type structure? Binary AB2 structure?

answer

8:8 and 8:4, CsCl, and CaF2

question

For a radius ratio of 0.414 to 0.732: What is the coordination number? Binary AB type structure? Binary AB2 structure?

answer

6:6 and 6:3, NaCl (ccp), NiAs (hcp), and TiO2

question

For a radius ratio of 0.225 to 0.414: What is the coordination number? Binary AB type structure? Binary AB2 structure?

answer

4:4, and ZnS (ccp and hcp)

question

radius ratio equation

answer

r small (cation)/ r large (anion)

question

alloys

answer

blends of metallic elements mixed in molten state and then cooled to form metallic solid

question

substitutional alloy

answer

similar atomic radii, same crystal structure, same electropositive nature (Ex: Alpha-brass, mix of Cu & Zn)

question

interstitial alloy

answer

smaller (dopants) atoms occupy voids (Ex: steel)

question

intermetallic alloy

answer

resemble neither parent atoms structure, high melting points, hard, and brittle (Ex: Beta brass)

question

defects

answer

vacant sites or misplaced atoms; this is thermodynamically favorable

question

Schotky defect

answer

intrinsic/point defect; pairs of ions are lost, so to maintain charge neutrality this happens; high coordination number and density change

question

Frenkel defect

answer

intrinsic/point defect; ions present are dislocated from original location and occupy interstitial spaces; have low coordination numbers

question

atom interchange/anti-site defect

answer

extrinsic defect; mutual exchange of atom positions based on P & T; neutral exchange; there is no change in coulombic repulsion because of the neutral exchange!

question

lattice formation enthalpy

answer

the enthalpy change when one mole of an ionic crystal lattice is formed from its isolated gaseous ions; energy is released so this is endothermic!

question

Hess's law equation

answer

delta Hf = everything added together

question

Hess's Law Definition

answer

the heat evolved or absorbed in a chemical process is the same whether the process takes place in one step or several steps (law of constant heat summation)

question

Born Mayer Equation

answer

1390 (zazb/do) * A* (1- d*/do) in kJ/mol where za = charge on ion A, zb = charge on ion B, do = distance between cations and anions in Angstroms, d* = exponential scaling factor for repulsive forces (0.345A)

question

Kapustkinsii Equation

answer

(1210) * (nzazb/do) * (1- d*/do); where n = the number of ions in the formula unit

question

electron sea model

answer

metallic bonds are strong electrostatic interactions that form between metal atoms and loosely bound electrons; the structure of metallic bonds is very different from that of covalent and ionic bonds; ionic bonds join metals to non metals and covalent bonds join non metals to non metals; metallic bonds are responsible for the bonding between metal atoms

question

density of state

answer

the number of energy levels per unit

question

Fermi level

answer

the highest occupied energy level in a solid at T = 0; energy level where the probability of finding an electron at absolute temperature

question

quantum confinement

answer

the effect describing the phenomenon resulting from electrons and electron holes being squeezed into a dimension that approaches a critical quantum measurement (Exciton Bohr Radius)

question

n dopant

answer

negative (excess electrons); dopant energy is closer to the conduction band

question

p dopant

answer

positive (donor is electron deficient and accepts electrons); dopant energy is closest to valence band because now the metal can inject electrons into the dopant band

question

coordination sphere

answer

formula written in square brackets (l in square bracket are connected to metal and those outside are free ions in solution); the central metal and ligands directly bound to it

question

ligand

answer

donor molecule or molecule (neutral anion) must donate pair of electrons to complete d orbital of metal

question

coordination compound

answer

metal complex that inoizes in a way so whats in the bracket is an ion and outside ion; compounds containing complexes

question

complex ion

answer

if charge remains on a metal complex

question

coordination

answer

coordinate covalent bond between L and M; orbital from a ligand with lone pairs overlaps with an empty orbital from a metal

question

central metal atom

answer

metal cation that gives different colors

question

complex

answer

a central metal atom bonded to a group of molecules or ions

question

Werner's Theory

answer

suggested that metal ions have primary and secondary valences

question

primary valence

answer

the metal's oxidation number

question

secondary valence

answer

the number of atoms directly bonded to the metal (CN)

question

monodentate

answer

1 donor atom with a lone pair

question

bidentate

answer

2 donor atoms per molecule

question

tridentate

answer

3 donor atoms per molecule

question

polydentate

answer

more than 6 or 7 donor atoms per molecule

question

ambidentate

answer

going to be a chance for either donor atoms or atom to coordinate based on nature of central metal atom

question

chelating agents

answer

have 2 or more donor atoms; bind to metal ions removing them from solution

question

porphoryins

answer

complexes containing a form of the porphine molecule; important biomolecules and form tetradentate or polydentate ligands

question

isomers

answer

same formula, different properties; have the same molecular formula, but their atoms are arranged either in a different order (structural) or spatial arrangement (stereo)

question

structural isomers

answer

different bonds (ionization, coordination, hydrate, and linkage)

question

stereoisomers

answer

same bonds, different spatial arrangements

question

linkage structural isomers

answer

linked through different ways to the central metal atom (ambidentate)

question

coordination sphere isomers

answer

differ in what ligands are bound to the metal and what is outside the coordination sphere

question

ionization isomers

answer

can be though of as occurring because of the formation of different ions in solution; exchange of ligands inside/outside the coordination sphere *example of a coordination sphere isomer!

question

hydrate isomer

answer

arises when one of the ligands is water; *example of a coordination sphere isomer!

question

cis isomer

answer

type of geometric isomer; have like groups on the same side

question

trans isomer

answer

type of geometric isomer; have like groups on the opposite side

question

geometric isomers

answer

same number of atoms, same bonding, different spatial arrangement

question

optical stereoisomers

answer

mirror images of eachother; cannot be superimposed on eachother, different interactions with polarized light

question

barry pseudorotation

answer

the flipping of geometry from square pyramidal to trigonal bipyramidal to reduce coulombic repulsion; only occurs with monodentate ligands!

question

meridional isomer

answer

geometric plane meridian, passes through the center of the complex

question

facial isomer

answer

forms 1 face of octahedron when line drawn between atoms

question

en

answer

All N ligands drawn

question

ox

answer

oxalate; all O atoms ligands drawn

question

glycine

answer

N & O drawn ligands (all o on one face and all n on the other)

question

Kf

answer

formation constant

question

multistep reaction general chemical equation

answer

M + nL = MLn

question

overall formation constant for multistep reaction

answer

Bn = [MLn] / [M][L]^n; Bn = Kf1*Kf2...Kfn

question

chelating effect

answer

increased local concentration with bidentate ligand with increased Kf (entropic); the greater stability of chelated complexes compared with their nonchelated analogues; results in an incrase in the number of independent molecules in solution

question

entropic

answer

makes delta G more negative

question

Macrocyclic effect

answer

has an enthalpic contribution; combination of the entropic effect seen in the chelate effect together with an additional energetic contribution that comes from the preoorganized nature of the ligating groups

question

disproportionation

answer

specific type of redox reaction in which a species is simultaneously reduced and oxidized to form two different products

question

comproportionation

answer

chemical reaction where 2 reactants, each containing the same element but dif oxidation number will form a product in which the elements involved reach the same oxidation number

question

depth of focus

answer

the distance over which the image plane can be displaced while a single object plane remains in acceptably sharp focus (due to resolution of electrons)

question

diffraction limit equation

answer

d = lambda/2NA

question

1 torr to pascals

answer

1 torr = 133.3 pascals

question

Thermionic electron gun

answer

Electrons are emitted when a solid is heated (tungsten wire, LaB6 crystal)

question

Field emission guns (FEG)

answer

Cold guns, a strong electric field is used to extract electrons (single crystal of tungsten etched to a thin tip) No heat, fine tungsten tip, single crystal of tungsten; an electric field is applied to a sharp tip and electrons are stripped via tunneling. Pass through high voltage with tunneling effect and allows electron beam interaction with sample

question

Schotky Emitters

answer

Sharp single crystal 100 tungsten tip with ZrO2 dopant to increase metal conductivity and change fermi level, combine heating and electric field and increases the conductivity at High temperatures

question

Condenser lens

answer

Controls spot size of sample (determines the beam current that impinges on the sample)

question

Objective lens

answer

Final probe forming focus, determined the final spot size of the electron beam (I.e. the resolution of an SEM)

question

Low convergence

answer

More beam accepted by aperture (spread of EM energy of beam), more current, less resolution

question

High convergence

answer

Less beam accepted by aperture (less current, higher resolution)

question

Focal length is proportional to..

answer

Magnetic field strength squared

question

Lorentz force

answer

The force exerted by a magnetic field on a moving electric charge

question

Lorentz force equation

answer

F = qEfield + (v * B); where F = force, q= charge on particle, V = velocity of electrons, and B = magnetic field

question

Electromagnetic lens

answer

Wound copper coil around soft iron pole-piece, applied current produces a magnetic field

question

Schematic x section

answer

Small slit in iron allows magnetic field to leak into column, current dictates field strength

question

Focusing action

answer

Electron trajectories change due to Lorentz force

question

electron tomography

answer

takes multiple images at varying angles with transmission electron microscopy; constructs into a 3D model

question

SE*secondary electron* (What is the energy? What is the range? What is the sensitivity?)

answer

<50 eV, few nm range, surface topography

question

BSE (What is the energy? What is the range? What is the sensitivity?)

answer

<PE, Partial voume, Material (avg Z)

question

Xray (What is the kinetic energy? What is the range? What is the sensitivity?)

answer

<PE, Full volume +, Element

question

Kanaya-Okayama Depth Perception Formula

answer

R = 0.0276AE^1.67/Z^0.89*p; where R = depth penetration, A = atomic weight (g/mol), E= beam energy, Z = atomic number, and P = density (g/cm^2)

question

secondary electrons

answer

low energy electrons ejected from the specimen atoms by the energetic primary beam

question

back scattered electrons

answer

primary beam electrons scattered back out of the sample

question

SEM holders

answer

with increase in precision, can rotate sample and get multiple images for 3D images

question

probe diameter

answer

diameter of spot

question

probe current

answer

# of electrons being generated per unit area

question

probe convergence angle

answer

broad beam focusing more narrowly down

question

accelerating voltage

answer

gives direct correction to resolution, depth of focus and image quality

question

optical brightness ratio formula

answer

Beta = current/area*solid angle

question

disc of least confusion

answer

very narrow range of kinetic energy and beam able to interact with sample

question

raster pattern

answer

samples the specimen surface point to point over the scanned area

question

secondary electron detector

answer

consists of a Faraday cage which accelerates electrons toward a scintillator (converting into light); produces a current which is directed toward a PMT and the amplified signal is read on the monitor

question

electron wavelength equation

answer

lambda = 12.3 A/SQRT(mV); where mV =momentum

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