Inorganic Chemistry Exam 3

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tetrahedral void
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0.225r
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octahedral void
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0.414r
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cubic void
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0.732r
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Polymorphism
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The ability to adopt different crystal forms under different conditions of pressure and temperature
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Alloy
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Blend of metallic elements prepared by mixing molten components and then cooling to produce a solid
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Interstitial solid solutions
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Formed between metals and small atoms that can occupy voids while maintaining crystal structure
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Rock salt structure
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Ccp array of bulky anions with cations in all octahedral holes with 6:6 coordination
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Cesium chloride structure
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Primitive cubic unit cell with each corner occupied by an anion and a cation occupying cubic hole at the center ; z=1
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Sphalerite/Zinc Blende
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Expanded ccp anion arrangement but actions occupy one type of td hole (1/2 holes present) 4:4 coordination, Z =4
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Wurtzite/Zinc Blende
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Derived from sphalerite but dorms expanded hcparray
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ZnS type 1
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zinc blende; FCC lattice arrangement (Ccp)
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ZnS type 2
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wurtzite; has an hcp packing lattice
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For a radius ratio of 1: What is the coordination number? Binary AB type structure? Binary AB2 structure?
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12; none known, none known
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For a radius ratio of 0.732 to 1: What is the coordination number? Binary AB type structure? Binary AB2 structure?
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8:8 and 8:4, CsCl, and CaF2
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For a radius ratio of 0.414 to 0.732: What is the coordination number? Binary AB type structure? Binary AB2 structure?
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6:6 and 6:3, NaCl (ccp), NiAs (hcp), and TiO2
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For a radius ratio of 0.225 to 0.414: What is the coordination number? Binary AB type structure? Binary AB2 structure?
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4:4, and ZnS (ccp and hcp)
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radius ratio equation
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r small (cation)/ r large (anion)
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alloys
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blends of metallic elements mixed in molten state and then cooled to form metallic solid
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substitutional alloy
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similar atomic radii, same crystal structure, same electropositive nature (Ex: Alpha-brass, mix of Cu & Zn)
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interstitial alloy
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smaller (dopants) atoms occupy voids (Ex: steel)
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intermetallic alloy
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resemble neither parent atoms structure, high melting points, hard, and brittle (Ex: Beta brass)
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defects
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vacant sites or misplaced atoms; this is thermodynamically favorable
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Schotky defect
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intrinsic/point defect; pairs of ions are lost, so to maintain charge neutrality this happens; high coordination number and density change
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Frenkel defect
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intrinsic/point defect; ions present are dislocated from original location and occupy interstitial spaces; have low coordination numbers
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atom interchange/anti-site defect
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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!
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lattice formation enthalpy
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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!
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Hess’s law equation
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delta Hf = everything added together
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Hess’s Law Definition
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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)
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Born Mayer Equation
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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)
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Kapustkinsii Equation
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(1210) * (nzazb/do) * (1- d*/do); where n = the number of ions in the formula unit
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electron sea model
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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
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density of state
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the number of energy levels per unit
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Fermi level
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the highest occupied energy level in a solid at T = 0; energy level where the probability of finding an electron at absolute temperature
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quantum confinement
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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)
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n dopant
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negative (excess electrons); dopant energy is closer to the conduction band
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p dopant
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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
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coordination sphere
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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
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ligand
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donor molecule or molecule (neutral anion) must donate pair of electrons to complete d orbital of metal
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coordination compound
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metal complex that inoizes in a way so whats in the bracket is an ion and outside ion; compounds containing complexes
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complex ion
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if charge remains on a metal complex
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coordination
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coordinate covalent bond between L and M; orbital from a ligand with lone pairs overlaps with an empty orbital from a metal
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central metal atom
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metal cation that gives different colors
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complex
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a central metal atom bonded to a group of molecules or ions
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Werner’s Theory
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suggested that metal ions have primary and secondary valences
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primary valence
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the metal’s oxidation number
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secondary valence
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the number of atoms directly bonded to the metal (CN)
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monodentate
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1 donor atom with a lone pair
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bidentate
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2 donor atoms per molecule
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tridentate
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3 donor atoms per molecule
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polydentate
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more than 6 or 7 donor atoms per molecule
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ambidentate
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going to be a chance for either donor atoms or atom to coordinate based on nature of central metal atom
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chelating agents
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have 2 or more donor atoms; bind to metal ions removing them from solution
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porphoryins
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complexes containing a form of the porphine molecule; important biomolecules and form tetradentate or polydentate ligands
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isomers
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same formula, different properties; have the same molecular formula, but their atoms are arranged either in a different order (structural) or spatial arrangement (stereo)
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structural isomers
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different bonds (ionization, coordination, hydrate, and linkage)
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stereoisomers
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same bonds, different spatial arrangements
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linkage structural isomers
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linked through different ways to the central metal atom (ambidentate)
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coordination sphere isomers
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differ in what ligands are bound to the metal and what is outside the coordination sphere
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ionization isomers
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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!
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hydrate isomer
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arises when one of the ligands is water; *example of a coordination sphere isomer!
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cis isomer
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type of geometric isomer; have like groups on the same side
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trans isomer
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type of geometric isomer; have like groups on the opposite side
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geometric isomers
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same number of atoms, same bonding, different spatial arrangement
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optical stereoisomers
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mirror images of eachother; cannot be superimposed on eachother, different interactions with polarized light
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barry pseudorotation
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the flipping of geometry from square pyramidal to trigonal bipyramidal to reduce coulombic repulsion; only occurs with monodentate ligands!
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meridional isomer
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geometric plane meridian, passes through the center of the complex
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facial isomer
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forms 1 face of octahedron when line drawn between atoms
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en
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All N ligands drawn
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ox
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oxalate; all O atoms ligands drawn
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glycine
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N & O drawn ligands (all o on one face and all n on the other)
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Kf
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formation constant
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multistep reaction general chemical equation
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M + nL = MLn
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overall formation constant for multistep reaction
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Bn = [MLn] / [M][L]^n; Bn = Kf1*Kf2…Kfn
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chelating effect
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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
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entropic
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makes delta G more negative
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Macrocyclic effect
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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
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disproportionation
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specific type of redox reaction in which a species is simultaneously reduced and oxidized to form two different products
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comproportionation
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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
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depth of focus
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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)
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diffraction limit equation
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d = lambda/2NA
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1 torr to pascals
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1 torr = 133.3 pascals
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Thermionic electron gun
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Electrons are emitted when a solid is heated (tungsten wire, LaB6 crystal)
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Field emission guns (FEG)
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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
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Schotky Emitters
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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
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Condenser lens
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Controls spot size of sample (determines the beam current that impinges on the sample)
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Objective lens
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Final probe forming focus, determined the final spot size of the electron beam (I.e. the resolution of an SEM)
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Low convergence
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More beam accepted by aperture (spread of EM energy of beam), more current, less resolution
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High convergence
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Less beam accepted by aperture (less current, higher resolution)
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Focal length is proportional to..
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Magnetic field strength squared
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Lorentz force
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The force exerted by a magnetic field on a moving electric charge
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Lorentz force equation
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F = qEfield + (v * B); where F = force, q= charge on particle, V = velocity of electrons, and B = magnetic field
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Electromagnetic lens
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Wound copper coil around soft iron pole-piece, applied current produces a magnetic field
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Schematic x section
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Small slit in iron allows magnetic field to leak into column, current dictates field strength
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Focusing action
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Electron trajectories change due to Lorentz force
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electron tomography
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takes multiple images at varying angles with transmission electron microscopy; constructs into a 3D model
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SE*secondary electron* (What is the energy? What is the range? What is the sensitivity?)
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<50 eV, few nm range, surface topography
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BSE (What is the energy? What is the range? What is the sensitivity?)
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<PE, Partial voume, Material (avg Z)
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Xray (What is the kinetic energy? What is the range? What is the sensitivity?)
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<PE, Full volume +, Element
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Kanaya-Okayama Depth Perception Formula
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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)
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secondary electrons
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low energy electrons ejected from the specimen atoms by the energetic primary beam
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back scattered electrons
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primary beam electrons scattered back out of the sample
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SEM holders
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with increase in precision, can rotate sample and get multiple images for 3D images
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probe diameter
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diameter of spot
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probe current
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# of electrons being generated per unit area
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probe convergence angle
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broad beam focusing more narrowly down
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accelerating voltage
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gives direct correction to resolution, depth of focus and image quality
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optical brightness ratio formula
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Beta = current/area*solid angle
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disc of least confusion
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very narrow range of kinetic energy and beam able to interact with sample
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raster pattern
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samples the specimen surface point to point over the scanned area
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secondary electron detector
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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
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electron wavelength equation
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lambda = 12.3 A/SQRT(mV); where mV =momentum

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