Inorganic Chemistry ACS: Study Guide

Ionization energy

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

periodic trend of ionization energy

highest at top right-smaller electron=harder to remove

Why is a half filled subshell so stable?

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

exchange interaction

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

pairing energy

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

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

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

What happens when a 3d series metal is ionized?

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

lanthanide contraction

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

lanthanides

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

Slater's rules

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)

Shielding

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

penetration

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

electron affinity

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

Combination of electron affinity and ionization energy

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

polarizability

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

Why do we use the hydrogen system approximation

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

What is the formula for the energy of a hydrogen orbital

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

Energy can be expressed in...

Joules, wavenumber, inverse centimeters

quantum number N

principle quantum number, defines energy and size of orbital

quantum number L

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.

quantum number Ml

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

quantum number Ms

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

Radial wavefunction

(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

Radial distribution function

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

Bohr radius

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

What orbitals correspond to l=0 through l=4

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

Building up principle/Hund's rule

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

Pauli exclusion principle

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

Descibe VSEPR

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.

Relative repulsion strengths VSEPR

lone pair> multiple bonds> single bonds

Valence bond theory

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

How is hybridization used in valence bond theory

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

Effect of a lone pair on geometry?

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

Molecular orbital theory

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

MO theory assumptions

orbital approximation, linear combinations of atomic orbitals

Orbital approximation

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

linear combination of atomic orbitals

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

H2 and H2-like molecules

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

Li2 through N2 (period 2)

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

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

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

H-X

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

X-Y

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

Relative energies of MOs

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

Plyatomic MO

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

LCAO notation

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

LCAO energies

lowest=a (nondegenerate)

intermediate=e

highest=t

LCAO

linear combinations of atomic orbitals

Bond order

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

Calculating bond order

(bonding-antibonding)/2

How to assign bonding character-bonding

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

How to assign bonding character-nonbonding

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

How to assign bonding character-antibonding

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

HOMO interactions

highest occupied molecular orbital, highest energy electrons reside

LUMO interactions

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

Importance of HOMO/LUMO

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

paramagnetism

if there are two unpaired electrons

metallic bonding

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

ionic bonding

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

lattice

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

unit cell

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.

7 types of crystal systems

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

Primitive unit cell

contains only one lattice point

body centered

two lattice points per unit cell

face centered

four lattice points per unit cell

body centered cubic

3D version of body centered

close packed

structure type with least unfilled space

coordination number

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

cubic close packed

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

face centered cubic

same thing as cubic close packed

hole

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

polymorphism

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

alloy

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

substitutional solution

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

interstitial solid solution

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

lattice enthalpy

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

born haber cycle

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

van der waals interaction

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

non-stoichiometric compound

substance that exhibits variable composition but retains the same structure type

conductor

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

semi conductor

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

insulator

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

super conductor

have zero resistance below a critical temperature

band

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

band gap

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

s/p band

the bands built from s and p orbitals

fermi level

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

parameters for a substitutional solid solution?

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

parameters for an interstitial solid solution

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)

Most stabilizing influence on a solid?

lattice enthalpy

high lattice enthalpy effect on solid

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

low lattice enthalpy effect on solid

is small charge and large distance the solid is not stable

born mayer equation

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

Why does solubility depend on lattice enthalpy

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)

solvent levelling

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

Discuss band theory

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

band theory s band

forms between s orbitals

band theory p band

forms between p orbitals

conductors and band theory

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

insulators and band theory

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

types of semiconductors

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