question

Ionization energy

answer

energy required to remove the least tightly bound electron from a neutral atom in the gas phase

question

periodic trend of ionization energy

answer

highest at top right-smaller electron=harder to remove

question

Why is a half filled subshell so stable?

answer

it serves to maximize the stabilizing interactions while minimizing the destabilizing interactions among electrons

question

exchange interaction

answer

pie, stabilizing, result of electrons pairing in degenerate orbitals with parallel spin

question

pairing energy

answer

destabilizing, coulomb interaction, pic, energy of electron-electron repulsion in a filled orbital

question

Is it easier to ionize a high energy or low energy electrons

answer

high energy electron-already contains more energy so it requires less energy input

question

What happens when a 3d series metal is ionized?

answer

the first electron to be ionized will come from the 4s orbital, the other s electron will enter the d orbital (4s03dn+1)

question

lanthanide contraction

answer

reduction in atomic radius following the lanthanide series, contrary to the overall trend observed for the periodic table

question

lanthanides

answer

elements 57-71, first appearance of f orbitals, f orbitals are poor at shielding so any electrons dded will have a higher Zeff, shrinking the radius

question

Slater's rules

answer

tell us what the effective nuclear charge will be, Zeff=Z-sigma, Z is the atomic number, sigma=sum of the number of electrons in a given subtle multiplied by a weighting coefficient (page 1)

question

Shielding

answer

the reduction in charge attraction between the nucleus and electrons due to electrons between the nucleus and the electron in question, it is considered the be between if it has a lower energy

question

penetration

answer

when an electron of a higher atomic orbital is found within the shell of electrons of a lower atomic number, that is to say that an electron of higher energy is found within an orbital of lower energy

question

electron affinity

answer

the difference in energy for a neutral gaseous atom, and the gaseous anion. used interchangeably with electron gain enthalpy. more positive=more stable EA with the additional electron, more positive EGE=more stable with extra electron

question

Combination of electron affinity and ionization energy

answer

electronegativity, overall measure of an atoms ability to attract electrons to itself when part of a compound, fluorine has highest electronegativity

question

polarizability

answer

an atoms ability to be distorted by an electric field, regions of a molecule can take on partial positive or partial negative charge

question

Why do we use the hydrogen system approximation

answer

systems involving multiple electrons are much more complex, and they require the use of quantum mechanics

question

What is the formula for the energy of a hydrogen orbital

answer

E=-13.6(eV)*(Z^2/n^2), h is plancks constant (background on pg 4)

question

Energy can be expressed in...

answer

Joules, wavenumber, inverse centimeters

question

quantum number N

answer

principle quantum number, defines energy and size of orbital

question

quantum number L

answer

orbital angular momentum quantum number, defines the magnitude of the orbital angular momentum, as well as the angular shape of the orbital, L can have values of 0 to n-1.

question

quantum number Ml

answer

magnetic quantum number, describes the orientation of the angular momentum, ml can have values of 0 to +/-1

question

quantum number Ms

answer

spin magnetic quantum number, defines intrinsic angular momentum of an electron, Ms can have values of either +1/2 or -1/2

question

Radial wavefunction

answer

(R(r)), along with the angular wavefunction, gives us the orbitals. With a wave function it is possible to completely characterize a particle, goes to zero at infinity, produce characteristic shapes when graphed

question

Radial distribution function

answer

a plot of R^2(r)r^2, tells us probability of finding an electron at a certain distance from the nucleus, every orbital has a different radial distribution function and a node on the graph is a region of zero probability

question

Bohr radius

answer

the most probably distance to find the electron in a one proton, one electron system (52.9 pico-meters)

question

What orbitals correspond to l=0 through l=4

answer

L=0=s, L=1=p, L=2=d, L=3=f, L=4=g

question

Building up principle/Hund's rule

answer

when degenerate orbitals are available for occupation, electrons occupy separate orbitals with parallel spin

question

Pauli exclusion principle

answer

no more than two electrons can occupy a single orbital, and to do so, their spins must be paired

question

Descibe VSEPR

answer

purpose is to predict molecular geometries, basic assumption is that regions of enhanced electron density take positions as far apart as possible in order to minimize repulsive forces.

question

Relative repulsion strengths VSEPR

answer

lone pair> multiple bonds> single bonds

question

Valence bond theory

answer

explains chemical bonding by considering the overlap of tomic orbitals, wave patterns of atomic orbitals interfere constructively to form a bond, sigma is formed when orbital overlap has cylindrical symmetry, pi bond forms when they overlap side by side after the formation of a sigma bond

question

How is hybridization used in valence bond theory

answer

explains bonding where the number of equivalent bonds exceeds the number of valence orbitals

question

Effect of a lone pair on geometry?

answer

it pushes strongly against all other substituent. It is the strongest force governing the shape of a molecule

question

Molecular orbital theory

answer

an improvement over valence bond theory in that the bonding description extends to all atoms in a molecule and handles polyatomic molecules, atomic orbitals combine to form molecular orbitals which are delocalized descriptions of electron distribution

question

MO theory assumptions

answer

orbital approximation, linear combinations of atomic orbitals

question

Orbital approximation

answer

the wave function describing all of the electrons of a molecule can be written as a product of the one electron avefunctions

question

linear combination of atomic orbitals

answer

the superposition of multiple atomic orbitals of same type along with weighting coefficients

question

H2 and H2-like molecules

answer

the 1s orbitals are of equal energy so they lie at the same level of the diagram, atomic orbitals combine to form one sigma orbital which is lower in energy than one anti bonding sigma orbital which is higher in energy

question

Li2 through N2 (period 2)

answer

energy contributing to each atom is the same, 2s orbitals combine to form a bonding 1sigmag and an anti bonding sigmau, as well as a bonding 2sigmag, although that MO is mainly 2p in character. 2p combine as follows: lowest energy orbitals are two degenerates 1piu followed by 2sigmag. Following that is anti bonding orbital 1pig (doubly degenerate) ad 2sigmau

question

Period 2: O2, F2 etc, why not Ne2?

answer

difference is MO diagram's relative energies of the bonding orbitals piu and pig

question

H-X

answer

H is something that bonds through 2p and 2s orbitals, relative energies of the atomic orbitals are taken into account because there are two separate atoms, H1s is usually higher in energy, 4 atomic orbitals of X will mix with 1s of H to give 5 molecular orbital. Anti bonding is mostly H in character while the other 4 are mostly X

question

X-Y

answer

relative energies are taken into account, more electronegative=lower energy of orbitals

question

Relative energies of MOs

answer

4sigma>2pi>3sigma>1pi>2sigma>1sigma

question

Plyatomic MO

answer

must use approximations of MO theory. Linear combinations of Atomic orbitals create a cumulative approximation of the atomic orbitals of its constituent atoms, compare orbitals to determine what will mix

question

LCAO notation

answer

a,b=nondegenerate, e=doubly degenerate, t=triple degenerate

question

LCAO energies

answer

lowest=a (nondegenerate) intermediate=e highest=t

question

LCAO

answer

linear combinations of atomic orbitals

question

Bond order

answer

a method to assessing overall bond strength between two atoms in a molecule, higher bond order=stronger bond, assesses net number of bonds between two atoms

question

Calculating bond order

answer

(bonding-antibonding)/2

question

How to assign bonding character-bonding

answer

a bonding orbital will lie lower in energy than its substituent atomic orbitals

question

How to assign bonding character-nonbonding

answer

a nonbonding orbital will equal in energy to its corresponding atomic orbitals

question

How to assign bonding character-antibonding

answer

an antibonding orbital will lie higher in energy than its substituent atomic orbitals

question

HOMO interactions

answer

highest occupied molecular orbital, highest energy electrons reside

question

LUMO interactions

answer

lowest unoccupied molecular orbital, it is the energy level directly above the homo

question

Importance of HOMO/LUMO

answer

critical to electron structure, when excited an electron is promoted from HOMO to LUMO. bonding and anti bonding characteristics determine stability, the frontier orbitals are the point of interaction and basis of understanding for molecular interaction

question

paramagnetism

answer

if there are two unpaired electrons

question

metallic bonding

answer

the bonding and ordering of metals into pure solids or solid solutions, viewed as enormous molecules with continually overlapping atomic orbitals

question

ionic bonding

answer

ions of different elements held together in rigid, symmetrical arrays as a result of attraction between their opposite charges

question

lattice

answer

a 3D infinite array of lattice points which define the repeating structure of a crystal

question

unit cell

answer

an imaginary, parallel sided region from which the entire crystal can be built, such that it fits perfectly together, giving rise to a crystal system.

question

7 types of crystal systems

answer

cubic, tetragonal, orthorhombic, monoclinic, triclinic, rhombohedral, hexaganol

question

Primitive unit cell

answer

contains only one lattice point

question

body centered

answer

two lattice points per unit cell

question

face centered

answer

four lattice points per unit cell

question

body centered cubic

answer

3D version of body centered

question

close packed

answer

structure type with least unfilled space

question

coordination number

answer

the number of nearest neighbors, number of other spheres that a single sphere is touching in the unit cell

question

cubic close packed

answer

ABCABC repeating layer of spheres (ABAB results in hexagonally close packed)

question

face centered cubic

answer

same thing as cubic close packed

question

hole

answer

unoccupied space between spheres, can be octahedral, where they lie between triangles and form a hexagon, or tetrahedral where it is formed by a planar triangle of touching spheres

question

polymorphism

answer

the ability of a metal to adopt different crystal structures based on the temperature and pressure

question

alloy

answer

a blend of different metals, more formally called a solid solution

question

substitutional solution

answer

when a solute metal atoms take up the positions of solvent metal atoms in the crystal structure

question

interstitial solid solution

answer

when the solute metal atoms take up positions in the holes of the solvent crystal structure

question

lattice enthalpy

answer

the standard enthalpy change of accompanying the formation of a gas of ions from a solid, measure of strength of the solid

question

born haber cycle

answer

a type of flow chart used to determine the lattice enthalpies and other parameters governing how a solid behaves

question

van der waals interaction

answer

non electrostatic contributions to the lattice enthalpy, the london dispersion interaction is the most dominant VDW interaction, the transient fluctuations in electron density that result in temporary, induced dipoles

question

non-stoichiometric compound

answer

substance that exhibits variable composition but retains the same structure type

question

conductor

answer

a substance with an electric conductivity that decreases as temperature is increased

question

semi conductor

answer

a substance with an electric conductivity that increases as temperature is increased

question

insulator

answer

negligible conduction, but if it is possible to measure, it increases with temperature

question

super conductor

answer

have zero resistance below a critical temperature

question

band

answer

a near continuous array of energy levels, due to the large number of symmetrically oriented atomic orbitals in a solid with very similar energy levels

question

band gap

answer

a separation of bands, due to there being no energy value for the molecular orbital

question

s/p band

answer

the bands built from s and p orbitals

question

fermi level

answer

the highest occupied energy level in a solid at T=0

question

parameters for a substitutional solid solution?

answer

atomic radii of elements are within 15% of each other, crystal structures of two pure metals are the same (directional forces are compatible), electropositive characteristics of both compounds are similar, otherwise electron transfer would be likely

question

parameters for an interstitial solid solution

answer

usually form between metals and small groups, small atom must not transfer electrons or there would be an ionic species, must have a radius all enough to fit in the hole (.414 * radius of metal)

question

Most stabilizing influence on a solid?

answer

lattice enthalpy

question

high lattice enthalpy effect on solid

answer

if high charge and small distance, strongly stabilizing, at highest when tightly packed and ion charge is dense

question

low lattice enthalpy effect on solid

answer

is small charge and large distance the solid is not stable

question

born mayer equation

answer

allows us to estimate the lattice enthalpy from charge and separation at T=0

question

Why does solubility depend on lattice enthalpy

answer

solubility is a product of enthalpy and hydration enthalpy. lattice enthalpy is the energy required to break apart an ionic solid so the solubility is dependent on that value. If thee is a large difference between ionic sizes, the compound is likely to be soluble in water because the ways in which lattice enthalpy and hydration enthalpy depend on the radius (difference in size increases=lattice enthalpy decreases=hydration enthalpy increase)

question

solvent levelling

answer

the ordering of water molecules around a dissolved ion. the more charge dense an ion is, the more it order the water. This is entropically unfavorable, so it acts against processes that seek to break apart ions in solution

question

Discuss band theory

answer

connected to MO theory, continuum of overlapping orbitals, lowest energy orbitals have no nodes between neighboring atoms, highest energy orbitals have nodes between every pair of neighbors, the energy separation between neighboring orbitals approaches zero, creating a near continuous energy spectrum

question

band theory s band

answer

forms between s orbitals

question

band theory p band

answer

forms between p orbitals

question

conductors and band theory

answer

partially filled bands at low energy levels so the electrons are promoted easily, vigorous vibrations, such as those due to thermal energy, disrupt the band structure and decrease conductivity

question

insulators and band theory

answer

filled bands with a large energy differential separating them, filled band is called the valence band and the next higher band is called the conduction band

question

types of semiconductors

answer

intrinsic semiconductor, extrinsic semiconductor, n-type, p-type

question

intrinsic semiconductor

answer

filled s band and empty p band, energy gap is very small so the electrons can be promoted by thermal energy, promotion of electrons results in positive holes in the valence band amounting to a charge separation, which allows current to flow,

question

extrinsic semiconductor

answer

a material gains the ability to be a semiconductor because of intentionally added impurities, which increase the number of electron carriers

question

N-type

answer

n means negative, dopant supplies additional electrons to the solid structure, these electrons like below the valence band in energy and close to the conduction band so the gap is much easier to jump

question

P-type

answer

p means positive, the dopant material has less valence electrons than the parent material. the holes it creates lie just above the valence band in energy, so electrons can jump to the acceptor band to allow current to flow

question

what conditions are needed for electrons to flow through a solid

answer

a small energy difference and unfilled orbitals

question

lewis acid

answer

electron pair acceptor

question

lewis base

answer

electron pair donor

question

bronsted lowry acid

answer

proton donor

question

bronsted lowry base

answer

proton acceptor

question

hard acids bond in order of

answer

I<Br<Cl<F

question

soft acids bond in order of

answer

F<Cl<Br<I

question

soft acids/soft bases

answer

larger, more polarizable

question

hard acids/hard bases

answer

smaller and more charge dense

question

HSAB bonding patterns

answer

hard acids/bases to hard acids/bases, soft to soft

question

How does covalence apply to HSAB

answer

cation covalence increases as size of anion increases, anion covalence increases and size of cation decreases, covalence increases as charge increases, covalence in larger for non-noble configurations

question

what contributes to the gibbs energy of complex formation? (other than type of bond formed)

answer

competition with solvent, rearrangement of subsituents of the acid and base that may be necessary for formation of the complex, steric repulsion between substituents on the acid and base

question

criteria for categorization of HSAB

answer

no definite criteria, based on experimentally determined evidence usually relating to complex formation

question

amphiprotic substance

answer

a molecule that can act as both a bronsted acid and base

question

relationship between a strong acid and its conjugate base

answer

strong acid will have a weak conjugate base, strong base will have a weak conjugate acid, strong acid will remain deprotonated, strong base remains protonatedKa

question

Ka for a bronsted acid

answer

Ka=([A-][H3O+])/[HA]

question

range and meaning of Ka

answer

high Ka=one introduced to the solution, HA immediately and completely converts to A- and H3O+ (except for one in every Ka value (10^11 in case of HI)). Strong acids have high Ka and weak acids have small Ka, where almost no molecules lose a proton

question

autoprotolysis

answer

the proton transfer from one water molecule to another

question

why is autoprolysis easier to calculate

answer

it establishes a constant equilibrium, even in neutral water, between hydronium and hydroxy ions, so KaKb=Kw and Kw=[H3O][OH]

question

Discuss proton affinity and proton gain enthalpy

answer

proton affinity (Ap) and proton gain enthalpy (delta ph H naught), relate to acidity enthalpy changes during a proton transfer.PGE is reported as positive and PA is the negative of it. High AP indicated strong basicity, if only slightly negative, it is only weakly basic or possibly acidic

question

Proton gain 3 steps

answer

electron loss, electron gain, combination of H and A, reverse of H-A bond dissociation, proton gain enthalpy is the sum of the enthalpy of all of these steps

question

dominant factor in determining acid character

answer

electron affinity=inversely related to proton affinity, Ae increases left to right, proton affinity increases right to left, as proton affinity decreases, acidity increases, so Ae and stronger acid character have a positive and direct correlation. higher Ae=more stable conjugate base

question

discuss solvent levelling

answer

solvent levelling in water is the fact that any strong acid or strong base in aqueous solution is only as strong of an acid as h3O+, or as strong as a base of OH-. relative strengths of strong acids can be measured by using an anhydrous weak acid as the solvent, same idea can be applied to bases

question

equations for Ka and Kb when considering solvent leveling of water

answer

Ka=([H2Sol][A])/[HA], Kb=([HB][Sol])/[B]

question

How is the bronsted definition of aids and bases extended by the solvent system definition

answer

bronsted definition is only concerned with proton transfer, solvent system defines an acid as any solute that increases the concentration of the cation generated by auto ionization of the solvent. Defines a base as anything that increases the concentration of the anion generated by the auto ionization of the solvent

question

aqua acids

answer

the acidic proton on a water molecule coordinated to the central metal ion

question

discuss aqua acids

answer

acid strength increases as the covalent character of the M-O(H2) bond increases. Across the periodic table, covalence increases left to right, top to bottom. General, the heavier the metal, the stronger the acid will be

question

define and discuss hydroxoacids

answer

the acidic proton is from a hydroxyl group coordinated to a central metal ion, but without a neighboring oxo group

question

define and discuss oxo-acids

answer

the acidic proton is from a hydroxyl group coordinated to a central metal ion, with an oxo-group adjacent to it. stability of conjugate base if primary factor in determining acid strength, conjugate base's stability is determined by resonance, polarizability and charge density

question

oxo acid generalizations

answer

non metals form acidic oxides because electronegativity, metals form basic oxides, going down a group, atoms are bigger, polarizes water better and higher hydration enthalpy and entropy, amphoteric compounds form weak acids and weak bases, bases donate electron density, HSAB makes conjugate less stable by making it more soluble

question

types of non aqueous solvents

answer

liquid ammonia, hydrogen fluoride, anhydrous sulfuric acid, dinitrogen tetroxide

question

lewis acidity in alkali metals

answer

act as lewis acid in water, forming hydrated ions

question

lewis acidity in group 13

answer

boron tri-halides act as lewis acids, acid strength increases with atomic mass of the halogen, aluminum halides form dimers in the gas phase, and are used as lewis acid catalysts

question

lewis acidity in group 14

answer

except carbon, group 14 elements exhibit hypervaalence and act as lew acids, tin (II) chloride acts as both a lewis acid and a lewis base

question

lewis acidity in group 15

answer

oxides and halides of the heavier elements act as lewis acids

question

group 16

answer

sulfur dioxide can act as a lewis base when it forms a complex with trialkylamine that acts as a lewis base, sulfur trioxide is a strong lewis acid

question

halogens

answer

bromine and iodine act as mild lewis acids

question

difference between hard-hard and soft-soft interactions

answer

H-H and S-S are more thermodynamically stable than H-S, S-S is more covalent in character, H-H is more ionic in character, S-S are more exothermic

question

factors influencing the gibbs energy of complex formation

answer

competition with solvent, rearrangement of substituents, steric repulsion

question

reduction

answer

gain of electrons

question

oxidation

answer

loss of electrons

question

reducing agent

answer

the species which supplies the electrons (it is oxidized)

question

oxidizing agent

answer

the species which receives the electrons (it is reduced)

question

redox couple

answer

reducing agent + oxidizing agent

question

significance of oxidation numbers

answer

used to describe the ionic state of an atom

question

why do we write half reactions to express reduction potentials?

answer

it follows the movement of electrons, breaking a reaction into half reactions to separate reduction and oxidation gives us a clear view of electron transfer , and simplifies balancing a reaction

question

Why is the electrochemical series so hard to predict

answer

it involves a number of thermochemical cycles, including heat of sublimation, ionization energy, standard enthalpy of hydrations, none dissociation energy, and the overall reaction enthalpy

question

effect of multiplying a half reaction

answer

does not change potential but does change the free energy

question

what values of K and E indicate a spontaneous reaction

answer

if E>0 and K>1 the thermodynamics are favorable (spontaneous)

question

anode

answer

site of oxidation

question

cathode

answer

site of reduction

question

galvanic cell

answer

an electrochemical cell in which a reaction drives an electric current which travels though an external circuit for measurements

question

equation for gibbs free energy involving the standard cell potential

answer

Delta G naught=-nFEnaught, F=9.648*10^4 (faraday) and n is the number of electrons

question

strong oxidizing agent

answer

E naught is large and positive

question

strong reducing agent

answer

E naught is large and negative

question

Nernst equation

answer

gives cell potential at any composition, gives delta r G value,

question

under what conditions might a reaction be thermodynamically favorable but kinetically slow

answer

if E naught > 0, it is spontaneous, but if it requires the movement of multiple electrons simultaneously it will be slow

question

discuss the pH dependence of redox reactions

answer

as pH increases, E decreases. As pH decreases, E increases, this is due to the fact that any redox reactions require H+ ions, and a greater abundance of them increase the amount of current that can be transferred

question

passivating layer

answer

kind of 'skin' of a metal oxide that forms over a metal's surface, which protects the metal from reacting further, forms when the metal begins to react with water or acid and sticks to it, encapsulating it. not necessarily used but utilized so that the metal will not corrode in open air

question

what conditions will make water an oxidizing agent

answer

this will happen spontaneously if the metal is from the s-block, group 3 to group 9, or a lanthanoid. If the standard reduction potential for a metal is negative, it will be oxidize by 1M acid. H2 forms as the reaction progresses

question

what conditions will make water a reducing agent

answer

if the standard reduction potential for a redox couple is 1.23 V or higher, they can oxidize water. Because H+ is produced in the reaction, a higher pH encourages formation of the products, these types of actions are spontaneous but kinetically very slow because the number of electrons that need to be moved

question

stability field of water

answer

the range of values of potential for which water is thermodynamically stable toward both oxidation and reduction, stable between pH 4 and pH 9, between redox potentials of H+/H2, O2/H2O

question

Under what conditions will water be unstable

answer

it will be unstable outside of the boundaries previously stated

question

disproportionation

answer

the oxidation number of an element that is simultaneously raised and lowered, such that a species at a certain oxidation state is converted to a species that is more oxidize, and a species that is reduced. In a latimer diagram, if the potential on the right is higher than the potential on the left, it will tend to disproportionate

question

comproportionation

answer

the reverse of disproportionation, two species of the same element n different oxidation states will form a common product of the same oxidation state. In a latimer diagram, if the potential on the left is higher than that on the right, it will tend to comproportionate

question

How would i use the standard cell potential to determine the solubility product

answer

if an aqueous metal ion and its precipitate are in equilibrium, the solubility product (Kip) can be determined by the reduction potentials for the half reaction that returns the metal to its neutral state, both as an individual ion and as the precipitate

question

latimer diagram

answer

a type of flow chart that are used to follow the oxidation and reduction of a particular element or compound, can be used to quickly determine the number of electrons transferred in a redox reaction, and it gives the standard potentials associated with them

question

symmetry operator E

answer

identity operator, always there

question

symmetry operator Cn

answer

rotation by 360/2, if n=2, only one operation involved. if n=3, two operations associated with it, principal axis

question

principal axis

answer

the highest order rotational axis and it defines the z-axis of the molecule

question

symmetry operator sigma mirror plane

answer

a mirror plane is a vertical mirror plane, sigmav, is it contains the z-axis, as defined by rotational symmetry. The horizontal mirror plane, sigmah, is the plane of the molecule perpendicular to sigmav, there can also be a dihedral mirror plane, sigmad, which bisects two c2 axes

question

symmetry operator I

answer

center of inversion, inversion operator has each atom of the molecule projected through a single point, and out the same distance on the other side, succeeding to interchange diametrically opposite in pairs, only Oh, Dinfinityh, D4h, D2h, and Ci point groups have an inversion operator

question

symmetry operator Sn

answer

improper rotation/ screw axis. This consists of a rotation through a certain angle followed by a reflection in a mirror plane perpendicular to the rotation

question

high symmetry groups

answer

Dinfinityv, Cinfinityv, Ih, Oh, Td

question

low symmetry groups

answer

Cs, Ci, C1

question

irreducible representation

answer

the row of characters for the given symmetry species

question

symmetry in a polar molecule

answer

3 rules to account for permanent dipole, cannot be polar if it has a center of inversion (Oh, DInfinityh, D4h, D2h, Ci), cannot have an electric dipole moment perpendicular to any mirror plane, molecule cannot have an electric dipole moment perpendicular to any axis of rotation

question

symmetry in a chiral molecule

answer

a molecule cannot be chiral if it has an improper rotation axis or a mirror plane

question

relationship between degrees of freedom and character tables

answer

for molecule of N atoms, there are 3N degrees of freedom, 3 are translational, 3 are rotational, 3N-6 vibrational modes (if non linear) if linear, there is no rotation about the axis of the molecule so there are 3N-5 vibrational modes in a linear molecule

question

IR active

answer

the symmetry species of the vibration must be the same as that of x, y, or z in the character table

question

Raman active

answer

the symmetry species of the vibration must be the same as that of xy or x^2

question

SALC

answer

symmetry adapted linear combination of atomic orbitals, atomic orbitals which can be combined to a single symmetry type in order to construct a MO diagram

question

how does an irreducible representation help us identify Raman active and IR active

answer

if a molecule has a center of inversion, none of its nodes can be both IR and Raman active, an active vibrational mode is IR active if it has the same symmetry as a component of the electric dipole moment (x,y,z rotations). A vibrational mode is Raman active if it has the same symmetry as a component of the molecular polarizability (quadratic functions)

question

nomenclature of coordination compounds

answer

to write a formula, cation then anion followed by ligands in alphabetical order. to name the compounds, first the ligands are listed alphabetically (with prefix) then followed by the metal and its charge. if there is bridging it has µ

question

mono

answer

one point of attachment

question

bi

answer

two points of attachment

question

tri

answer

three points of attachment

question

how do you identify mono-bi-ti dentate ligands

answer

the atoms which bind to the central metal typically have lone pairs, or carry a negative charge. It is important to note that carbon is rarely the site of attachment

question

ambidentate ligand

answer

one which has multiple donor atoms, but only binds through one, typically has a negative charge, resonance stabilized

question

chelate

answer

a complex which forms when a polyentate ligand binds to a metal with more than one of it's donor atoms. They tend to bind at adjacent sites in a cis configuration

question

in terms of coordination chemistry, what is an acid and what is a base

answer

metal ion is lewis acid (EP acceptor) and the ligand is a lewis base (EP donor)

question

Factors that govern the coordination number of a complex

answer

size of central atom or ion, steric interactions between ligands, electronic interactions between central atom/ion and ligands

question

Effect of large atomic radii on coordination number of complex

answer

larger radii=higher coordination numbers

question

what group on the periodic table known to form 2 coordinate complexes

answer

group 11

question

favored symmetry and point group for four coordinate complexes

answer

tetrahedral, a small cation and large ligands. If the ligands are the same the point group is Td. If central ion has a d8 configurations, it will adopt a square planar configuration if all the ligands are the same

question

favored symmetry and point group for five coordinate complexes

answer

uncommon, but if it does happen it will be square pyramidal (c4v) or trigonal bipyramidal (d3h). Steric distortions are common and deviations from ideal geometry happen frequently

question

favored symmetry and point group for six coordinate complexes

answer

almost always octahderal, Oh

question

for what atoms/ions will we observe high coordination numbers

answer

f block

question

four types of isomers

answer

linkage isomers, ionization isomers, hydrate isomers, coordination isomers

question

linkage isomers

answer

these form only with ambidentate ligands, and are the result of the different donor atom binding

question

ionization isomers

answer

these occur when a ligand and a counter-ion (dissolved in solution) change places

question

hydrate isomers

answer

occur when water trades places with a ligand

question

coordination isomers

answer

occur when two different complex ions can have the same molecular formula through different bonding orders

question

meridional and facial isomers

answer

only occur for 6 coordinate complexes with octahedral geometry with the formula MA3B3

question

meridional isomers

answer

have one set of ligands around the metal ion's meridian, the other set along the mermaid perpendicular to the other

question

facial isomers

answer

best visualized by putting all 3 of one ligand into a triangle and the other 3 into a diametrically opposite triangle

question

what isomers are observed for four coordinate complexes

answer

for square planar, on cis ad trans isomers occur. For tetrahedral, enantiomers are the only isomers

question

What isomers are observed for six coordinate complexes

answer

cis/trans, facial/meridional,

question

what is a formation constant and how is it determined

answer

an equilibrium constant denoted by Kf and is a measure of the strength of ligand binding relative to water. Large Kf=inds to incoming ligand well. Kf=[MLlittlen]/[M][L]

question

what is the trend of stepwise formation constants

answer

they tend to decrease with the addition of eah successive ligand

question

what causes a stepwise formation constant to deviate

answer

if Kf(n+1) is greater than Kfn it is indicative of a change in coordination, show that the complex is more stable at a lower coordination number than for the previous set of ligands

question

chelate effect

answer

a complex with chelating ligands is more stable than one with non chelating ligands, as observed by formation constants

question

What does the tanabe sugano diagram depict

answer

the energies of electronic states of complexes as a function of the ligand field strength. It shows terms splitting into different microstates

question

how are the term energies expressed on the axes

answer

E/B on y plotted against delta/B on x. B is rajah parameter

question

what does a curved line mean on a tanabe sugano diagram

answer

it is the result of mixing orbitals due to the same symmetry

question

what is the no crossing rule in a tanabe sugano diagram

answer

if the increasing ligand field causes two weak field terms to approach, they bend apart rather than cross

question

what is the name of the term of lowest energy, where is it on the graph?

answer

ground term, x axis

question

what spectrum does a tanabe sugano graph represent

answer

the electronic absorbance spectrum

question

what transition are forbidden on tanabe sugano

answer

transitions which change the spin state

question

what are the racah parameters

answer

the energy due to repulsions, and is expressed as a collection of 3 terms, A, B, and C. A is the average of total inter-electron repulsion, B and C are repulsion energies between individual d electrons

question

what is microstate

answer

micro states are the different ways in which electrons can occupy orbitals

question

what is a term

answer

spectroscopically distinguishable energy levels of micro states with the same energy when electron-electron repulsions are considered

question

how do electron-electron repulsions affect a spectrum

answer

they result in multiple absorptions, if they are treated as negligible then the micro states have the same energy

question

what energies are spin forbidden

answer

the lowest energies

question

what are the two most important properties of 3-d series and light elements (in order)

answer

relative orientation of electron spin, relative orientation of orbital angular momenta

question

big S

answer

S is the total spin quantum number, which comes from the relative orientations of individual spins

question

big L

answer

L is the total orbital angular momentum quantum number which comes from the relative orientation of individual orbital angular momenta of each electron

question

how do we assign values to L

answer

L can take on values of l1+l2, l1+l2-1...[l1-l2]

question

what is spin orbital coupling

answer

the relative orientation of spin and angular momenta of each electron

question

how do we assign values to S

answer

S can take on values of s1+s2, s1+s2-1...[s1-s2]

question

what are the ranges of ML and MS

answer

Ml can range from positive L to negative L so it encompasses 2L+1. MS can range from positive S to negative S so it encompasses 2S+1

question

russle saunders coupling

answer

used for 3d metals, the process of combining angular momenta by first summing spins, then orbital momenta, and combining them

question

What is the word for total spin? What is the abbreviation and how is it determined?

answer

total spin is called multiplicity, abbreviated with P,it is a 2S+1

question

describe the two steps using hund's rule to assign energies

answer

1. identify the micro state with the highest value of MS. This tells us the highest multiplicity. 2. Identify the highest permitted value of ML for the multiplicity. This tells us the highest L value for multiplicity. we are only concerned with the lowest energy, which is what this rule tells us how to find

question

how do you identify the ground term in a set of terms

answer

by using hund's rules

question

corresponding letter and orbital L=0

answer

S, A1g

question

corresponding letter and orbital L=1

answer

P, T1g

question

corresponding letter and orbital L=2

answer

D, T2g, Eg

question

corresponding letter and orbital L=3

answer

F, T2g, A2g, T1g

question

corresponding letter and orbital L=4

answer

G, A1g, Eg, T1g, T2g

question

What metal is L considered a very important factor?

answer

3d metals

question

for wat metals is L not a very important factor

answer

4d and 5d because spin, orbit coupling is the most important factor in determining energy

question

two types of charge transfers

answer

ligand to metal charge transfer, metal to ligand charge transfer

question

charge transfer

answer

occur when an electron that is primarily ligand or metal in character oigrates to an orbital that is primarily metal or ligand in character (opposite)

question

solvatochromism

answer

variation in the transition frequency with change in the solvent permittivity. this is a better indicator of a metal/ligand interaction than a ligand-ligand or metal-metal interaction

question

When do LMCT reactions occur in the visible region

answer

two causes, may be a result of the ligand having high energy lone pairs or because the metal has a low lying empty orbital

question

In a metal complex, what reduces what

answer

the ligand reduces the metal ion

question

are LCMT and MLCT localized or delocalized

answer

localized

question

what characteristics of the metal atom will give a strong CT band

answer

a metal ion with a high oxidation state

question

what characteristics of the complex makes a MLCT likely to occur

answer

if a complex has ligands with low lying pi star orbitals, especially with aromatics, a MLCT is likely to occur

question

describe the relative proximity of ligand and metal orbitals in a MLCT

answer

the metal d orbitals are low in energy, lying very close to the empty ligand orbitals

question

what are the most common ligands to result in MLCT

answer

diimines

question

Emax

answer

a measure of the absorption strength for ligand field transitions

question

what is the approximate Emax for octahedral complexes

answer

100

question

approximate Emax for tetrahedral

answer

250

question

approximate Emax for square planar

answer

100

question

transition dipole moment

answer

the impulse of a transition on an electromagnetic field, which is a measure of the strength of transitions

question

transition dipole moment for an allowed transition

answer

nonzero

question

transition dipole moment for a spin forbidden transition

answer

zero

question

describe spin allowed transitions in terms of a singlet to triplet transition and the value of ds

answer

singlet (s=0) cannot undergo reaction to triplet (s=1), it is a forbidden transition

question

what can relax the rules regarding spin transition

answer

spin orbital coupling can relax the spin transition rules, but these transitions are weak, although they do not increase with atomic mass

question

what are the laporte selection rules

answer

in a centrosymmetric molecule or ion, the only allowed transitions are those accompanied by a change in parity. Transitions from g to u in terms are allowed but those from g to g and u to u are forbidden. For s and d orbitals, forbidden transitions are s-s, p-p, d-d, f-f, s-d, p-f, while the allowed transitions are s-p, p-d, d-f

question

what can relax the laporte rules

answer

the selection rules are relaxed if the complex departs (slightly) from the perfect centrosymmetry in its ground state, or if asymmetric vibrations destroy the center of inversion

question

based on energies of the transition, classify them as spin and laporte allowed or forbidden

answer

E<1, SF (spin forbidden), LF (laporte forbidden) E<10 SA (spin allowed), LF E<100 SA, LF E<5000 SA, LA

question

ligand field splitting parameter

answer

the energy difference between sets of orbitals of different energy i the same sub shell

question

barycenter

answer

the energy level corresponding to a spherical distribution of electric charge

question

what will cause delta naught to increase

answer

it will increase with an increasing oxidation state, and down a group. Corresponds to smaller size having more highly charged ions which results in shorter metal-ligand bond distances

question

ligand field stabilization energy

answer

it is stabilizing energy imparted to a d orbital spltting into e.g. and t2g orbitals relative to the barycenter

question

pairing energy

answer

the coulomb repulsion that results from electrons pairing. Pairing energy is taken into account only when the pairing of electrons is in addition to that of a spherical field

question

define weak field a strong field cases

answer

weak field is when delta naught is less than P, strong field is when it is more than P. In the weak field case, the electron will be promoted to e.g. orbital and in the strong field case it will stay in t2g

question

high spin

answer

when there are now more electrons unpaired than in a free ion

question

low spin

answer

when there are more electrons paired than otherwise

question

for 3d ion complexes, considering the ligands, how do high spin and low spin correlate to the spectrochemical series

answer

low spin complexes generally have ligands that are high in the spectrochemical series, while high spin complexes generally have ligands that are low in the spectrochemical series

question

diamagnetic

answer

repelled by a magnetic field

question

paramagnetic

answer

attracted to a magnetic field

question

describe the orbital configuration for tetrahedral

answer

t2 orbitals are higher in energy than e orbitals, they are separated by delta t, with the t2 orbitals lying at 2/5 delta above the barycenter, and e orbitals at 3/5 below it. always high spin

question

describe the orbital configuration for square planar

answer

highest in energy is x2-y2, followed by xy, then yz, then zx, and z2 is the lowest energy. square planar is always higher energy than tetrahedral, favored for d8, low spin is favored

question

what will cause a molecule to experience the jahn teller effect

answer

it is cause by unstable geometry, but more specifically, electros with degenerate spin states in e.g. orbitals

question

what symmetries can we expect to see the jahn teller effect

answer

Oh, C4v, D4h

question

what effect does jahn teller distortion have on a spectra

answer

absorbance peaks wil be asymmetric, both are ground state and the excited state are detected so the peak may have a shoulder or overlapped peaks

question

what are the symmetry labels and degeneracy for a metal s orbital

answer

degeneracy of 1 a1g

question

what are the symmetry labels and degeneracy labels for a metal px, py, pz orbitals

answer

t1u, degeneracy of 3

question

what are the symmetry labels and degeneracy labels for a metal dx2-y2, dz2, orbitals

answer

e1, degeneracy of 2

question

what are the symmetry labels and degeneracy labels for a metal dxy, dyz, dxz orbitals

answer

t2g, degeneracy of 3

question

frontier orbitals

answer

molecular eg and t2g orbitals are the frontier orbitals. when considering only sigma bonding, the t2g molecular orbitals are entirely metal in character and non bonding

question

ligand pi orbitals include salcs of what symmetry

answer

t2g, it is delocalized

question

pi donor ligands are also known as what

answer

pi bases, they have filled pi orbitals about the M-L axis and are lower in energy than sigma orbitals

question

pi acceptor ligands are also known as what

answer

pi acids, they have empty pi orbitals available for occupation about the M-L axis

question

what electrons are ejected in X-ray absorbance spectroscopy

answer

electrons are ejected from the core

question

what is the range of energy for photons

answer

0.1 keV to 100keV

question

what does the photon energy correspond to

answer

related to binding energy of core electrons

question

what is the edge region

answer

where the photo electron energy is in the range of Ei-Ei+10eV

question

what is the K edge (pre edge)

answer

where the core electrons are not ejected but promoted to higher energy empty orbitals. It provides information on energies of excited electronic states and local symmetry if the atom

question

what is the continuum

answer

when referring to a continuous absorption spectrum, a continuum is where absorbance is shown continuously throughout a given range (think from initial to infinity)

question

how do dipole transitions appear in the spectra

answer

dipole transitions are forbidden

question

describe the XANES

answer

X ray absorption near edge fine structure, the energy lies between Ei and Ei+10eV. It gives information on oxidation state, coordination environment, and the subtle geometric distortions. It can be used as a fingerprint, as it is characteristic of the environment and valence state, ad also can be used to determine the presence and quantity of a compound in a mixture

question

Describe NEXAFS

answer

near edge X-ray absorption fine structure. The energy lies between Ei and Ei + 50eV. It gives information on the orientation of adsorbed molecules

question

EXAFS

answer

extended x-ray absorption fine structure. The energy range is anything greater than the NEXFAS region. The back scattering of photons by adjacent atoms can be detected by observing periodic trends in intensity at energies just above the absorption edge. It provides information on electron density, the number of nearby atoms, as well as the separation of atoms. It will also tell us the bond lengths of species in the amorphous samples

question

what are the relative strengths of dipole and quadripole transitions

answer

dipole transitions are bout 100 times stronger than the quadripole

question

define photoelectron spectroscopy (PES)

answer

the measurement of kinetic energies of electrons emitted by the ionization of a sample that is irradiated with high energy monochromatic radiation. More simply put, a sample is irradiated with a single wavelength light source, and this causes emissions of photoelectrons

question

what is the formula for PES

answer

Ek=hv-Ei

question

what is koopman's theorem

answer

the ionization energy is equal to the negative of the orbital energy

question

two types of PES

answer

x-ray photoelectron spectroscopy and UV photoelectron spectroscopy

question

XPS (x ray photoelectron spectroscopy)

answer

used to study the and structure of solids. Photons which cause ionizations in samples are photo electrons emitted from an anode. They photo electrons causing the ionization are the result of an ejection of a 1s electron, followed by a 2p electron moving down to fill the vacancy. XPS gives broad signals, half widths are about 1eV.

question

UPS (UV photoelectron spectroscopy)

answer

used the characterize valence shell energy levels and vibrational fine structure. The radiation source is a helium discharge lamp. smaller line widths

question

what does the spectra look like for an ion ejected from a non bonding orbital

answer

single, sharp line. Product is formed in its vibrational ground state

question

what does the spectra look like for an electron ejected from a bonding or anti bonding orbital

answer

extended fine structure with many peaks. it is formed in many vibrational states

question

how can we tell is the electron was ejected from a bonding or anti bonding orbital

answer

if it were ejected from a bonding orbital, it will have a lower frequency than the original molecule. If it were ejected from an anti bonding orbital, it will have a higher frequency than the original molecule

question

what causes peaks to appear on the spectra

answer

appear if the ejected electron has significant influence on geometry

question

what is electron paramagnetic resonance spectroscopy

answer

application of a magnetic field produces different energies in the magnetic angular orientation of electrons (+/- 1/2). We observe the resonant absorption of unpaired electrons

question

what types of atoms is EPR used to study

answer

paramagnetic species

question

what effect does the magnetic field have on the electron

answer

depending on the spin state, it will either raise or lower the energy and the energy difference is observed

question

describe a continuous wave spectrometer

answer

the sample is irradiated with a constant microwave frequency ad a varying magnetic field

question

how do you improve resolution, what causes improved resolution? EPR

answer

improved by using high magnetic fields, which reduces the interactions between paramagnetic centers, which sharpens and simplifies the spectra using pulsed EPR also makes higher resolution by providing time resolutions to make it possible to measure dynamic properties.

question

what is the G value EPR and what is it for a free electron

answer

the g value, or the londe factor, is the measure of the molecule or atom being studied. IT is a product of L, S, and J, the total angular momentum. G for fee electron = 2.0023

question

what perturbs the g value in compounds

answer

spin orbit coupling alters the g value in complexes

question

define isotropic

answer

all 3 g values are the same (along with 3 perpendicular axes)

question

define axial

answer

2 g values are the same

question

define rhombic

answer

all g values are different

question

why is resolution improved in frozen samples vs liquid

answer

in a liquid sample, the molecules are moving so they are difficult to measure

question

describe hyperfine structure

answer

it is a multiplet structure due to coupling of electron spin to magnetic nuclei. A nucleus with spin I will split the EPR line into 2I+1 lines of the same intensity

question

what is cyclic voltammeter and what does it tell us

answer

it tell us the redox potential of a complex and from that we can determine its stability. IT also gives us information of thermodynamic and kinetic properties. The current between two electrodes is measured as the potential difference and it is changed cyclically to produce a triangular waveform

question

working electrode metals

answer

Pr, Ag, Au, or graphite

question

reference electrode metals

answer

Ag/AgCl

question

what two critical species are contained in the solution, how concentrated are they?

answer

a redox couple wit a very dilute solution (micro molar)

question

first step CV

answer

the current is turned on and as it approaches the reduction potential of the redox couple, the reduced species is oxidized at the working electrode and the current starts to flow

question

step 2 CV

answer

the current rises to a peak then decreases as the reduced species is depleted

question

step 3 CV

answer

once the upper limit is reached, the sweep reverses

question

how do we approximate the redox potential

answer

the average of the 2 peaks is the approximate redox potential

question

what is the separation between the oxidation and reduction potential

answer

ideally they are separated by 59mV/#e-

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