Inorganic Chemistry Final Exam Study Guide

Inorganic Chemistry Final Exam Vocabulary Flashcards

Ionization Energy

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

Periodic Trend in Ionization Energy

Ionization energy is lowest at the bottom left corner of the periodic table and increases going up and to the right, with Helium having the highest ionization energy. This trend is similar to effective nuclear charge and atomic radii (smaller radius means higher ionization energy).

Exchange Interaction (πe)

A stabilizing interaction resulting from electrons pairing in degenerate orbitals with parallel spin.

Pairing Energy (πC)

A destabilizing interaction that represents the energy of electron-electron repulsion in a filled orbital (Coulomb interaction).

Ionization of 3d Series Metal

When a 3d series metal with a configuration of 4s23dn is ionized, the first electron is removed from the 4s orbital, resulting in the cation configuration 4s03dn+1.

Lanthanide Contraction

The reduction in atomic radius following the lanthanide series, due to poor shielding by f orbitals, leading to a higher effective nuclear charge (Zeff).

Slater's Rules

A method to approximate the effective nuclear charge (Zeff) experienced by an electron, calculated as Zeff = Z - σ, where Z is the atomic number and σ is the shielding constant.

Shielding

The reduction in charge attraction between the nucleus and electrons, caused by intervening electrons.

Penetration

The phenomenon where an electron in a higher energy atomic orbital is found within the shell of electrons in lower energy orbitals.

Electron Affinity

The difference in energy between a neutral gaseous atom and its gaseous anion. A more positive electron affinity indicates greater stability with the additional electron.

Electronegativity

The overall measure of an atom’s ability to attract electrons to itself when part of a compound.

Polarizability

An atom’s ability to be distorted by an electric field, allowing regions of a molecule to take on partial positive or partial negative charges.

Hydrogenic System Approximation

An approximation used because systems involving multiple electrons are complex and require quantum mechanics. The energy of a hydrogenic orbital is given by En = -13.6(eV)*(Z2/n2).

Radial Wavefunction

Along with the angular wavefunction, the radial wavefunction (R(r)) gives us the orbitals. These equations permit the characterization of a particle.

Radial Distribution Function

A plot of R^2(r)r^2 vs. radius, indicating the probability of finding an electron at a certain distance from the nucleus. A node on the graph indicates zero probability.

Bohr Radius

The most probable distance to find the electron in a one-proton, one-electron system, equal to approximately 52.9 picometers.

Aufbau Principle/Hund's Rules

When degenerate orbitals are available for occupation, electrons will occupy separate orbitals with parallel spin.

Pauli Exclusion Principle

No more than two electrons can occupy a single orbital, and if two electrons occupy the same orbital, they must have paired spins.

Valence Shell Electron Pair Repulsion (VSEPR) Theory

A theory used to predict molecular geometries based on the assumption that regions of enhanced electron density take positions as far apart as possible to minimize repulsive forces.

Valence Bond Theory

A theory explaining chemical bonding by considering the overlap of atomic orbitals, where constructive interference forms a bond.

Molecular Orbital (MO) Theory

An advanced bonding theory where atomic orbitals combine to form molecular orbitals, which are delocalized descriptions of electron distribution throughout a molecule. Includes the orbital approximation and Linear Combinations of Atomic Orbitals.

Bond Order

A measure of overall bond strength between two atoms in a molecule, calculated as B = 1/2(n - n), where n is the number of electrons in bonding orbitals and n is the number of electrons in antibonding orbitals.

HOMO

Highest Occupied Molecular Orbital; the orbital where the highest energy electrons reside.

LUMO

Lowest Unoccupied Molecular Orbital; the energy level directly above the HOMO.

Paramagnetism

Identified in a MO diagram by the presence of two unpaired electrons in the species.

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 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.

Coordination Number

The number of nearest neighbors of an atom in a crystal structure.

Hole

Unoccupied space between spheres in a crystal lattice.

Polymorphism

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

Alloy

A blend of different metals, also known as a solid solution.

Lattice Enthalpy

The standard enthalpy change accompanying the formation of a gas of ions from a solid; a measure of the strength of the solid.

Born-Haber Cycle

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

Van der Waals Interaction

Non-electrostatic contributions to the lattice enthalpy, with the London Dispersion interaction being the most dominant.

Non-stoichiometric compound

A 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

A substance with negligible conduction, but if it is possible to measure, it increases with 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.

Fermi Level

The highest occupied energy level in a solid at T=0.

Lewis Acid

An electron pair acceptor.

Lewis Base

An electron pair donor.

Bronsted Acid

A proton donor.

Bronsted Base

A proton acceptor.

Hard Acid/Base

Small and charge dense.

Soft Acid/Base

Large and more polarizable.

Amphiprotic Substance

A molecule that can act as both a Bronsted acid and base.

Autoprotolysis

The proton transfer from one water molecule to another, establishing a constant equilibrium between hydronium and hydroxyl ions.

Proton Affinity (AP)

The negative of the proton gain enthalpy (ΔpgH0), indicating basicity. A high AP indicates strong basicity.

Solvent Levelling

The effect where any strong acid or base in aqueous solution is only as strong as H3O+ or OH-.

Aqua Acids

The acidic proton is one a water molecule coordinated to the central metal ion.

Hydroxoacids

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

oxo-acids

The acidic proton is from a hydroxyl group coordinated to a central metal ion, with an oxo- group adjacent to it.

Reduction

The gain of electrons.

Oxidation

The loss of electrons.

Reducing Agent

The species which supplies the electrons (it is oxidized).

Oxidizing Agent

The species which receives the electrons (it is reduced).

Anode

The site of oxidation.

Cathode

The site of reduction.

Galvanic Cell

An electrochemical cell in which a reaction drives an electric current, which travels through an external circuit for measurements.

Nernst Equation

An equation giving the cell potential at any composition.

Passivating Layer

A kind of ‘skin’ of a metal oxide that forms over a metal’s surface, which protects the metal from reacting further. This layer forms when the metal begins to react with water or acid, and sticks to it, in effect encapsulating it.

Disproportionation

The oxidation number of an element is simultaneously raised and lowered, such that a species at a certain oxidation state is converted to a species that is more oxidized, and a species that is reduced.

Comproportionation

The reverse of disproportionation, two species of the same element in different oxidation states will form a common product of the same oxidation state.

Latimer Diagram

Latimer diagrams are a type of flow chart that are used to follow the oxidation and reduction of a particular element or compound. As seen here (and in 7d), a Latimer diagram can be used to quickly determine the number of electrons transferred in redox reaction, and it gives the standard potentials associated with them.

Symmetry Operator E

The identity operator. It’s always there.

Symmetry Operator Cn

Rotation by 360o/n. If n=2, there is only one rotation operation involved. If n=3, there are two operations associated with it, C3 and C3 ’ . There will always be n-1 rotational operations involved, only considering that axis. The principal axis is the highest order rotational axis, and it defines the z-axis of the molecule.

Symmetry Operator σ

Mirror plane. A mirror plane is a vertical mirror plane, σv, if it contains the z-axis, as defined by rotational symmetry. The horizontal mirror plane, σh, is in the plane of the molecule, or alternatively, perpendicular to σv. There can also be a dihedral mirror plane, σd, which bisects two C2 axes.

Symmetry Operator I

Center of Inversion. The inversion operation 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 pairs. Only Oh, D ∞h, , D4h, D2h, and Ci point groups have the inversion operator.

Symmetry Operator Sn

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

High Symmetry Groups

D∞v, C∞v, Ih, Oh, Td.

Low Symmetry Groups

Cs, Ci, C1.

Irreducible Representation

The row of characters for a given symmetry species in a character table.

SALC

A symmetry adapted linear combination of atomic orbitals, analogous to LCAO's, which are atomic orbitals that can be combined to a single symmetry type to construct a MO diagram.

Ligand

A molecule or ion that binds to a central metal atom to form a coordination complex.

Ambidentate Ligand

A ligand that has multiple potential donor atoms but only bonds to the cental metal through one at a time.

Chelate

A complex formed when a polydentate ligand binds to a metal with more than one of its donor atoms, usually at adjacent sites in a cis configuration.

Formation Constant (Kf)

An equilibrium constant that measures the strength of ligand binding relative to water.

Tanabe-Sugano Diagram

A diagram depicting the energies of electronic states of complexes as a function of ligand field strength.

Spin Forbidden Transitions

Transitions which change the spin state.

Microstate

The different ways in which electrons can occupy orbitals.

Term

Spectroscopically distinguishable energy levels of microstates with the same energy when electron-electron repulsions are considered.

Multiplicity

Total spin, abbreviated with P. It is 2S+1.

Charge Transfer

The movement of electronic charge from one part of a molecule (or complex) to another; transition occurs when an electron that is primarily ligand (or metal) in character migrates to an orbital that is primarily metal (or ligand) in character.

Ligand to Metal Charge Transfer (LMCT)

A type of charge transfer where an electron migrates from an orbital that is primarily ligand to an orbital that is primarily a metal.

Metal to Ligand Charge Transfer (MLCT)

A type of charge transfer where an electron migrates from an orbital that is primarily metal in character to an orbital that is primarily ligand in character.

Laporte Selection Rules

Rules stating that for centrosymmetric molecules, only transitions accompanied by a change in parity are allowed (g to u transitions).

Ligand Field Stabilization Energy (LFSE)

The stabilizing energy imparted to a d orbital splitting into eg and t2g orbitals relative to the barycenter.

Pairing Energy (P)

The coulombic 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.

High Spin

more electrons are unpaired than in a free ion (spherical electron distribution).

Low Spin

more electrons paired than otherwise.

Diamagnetic

Compounds that are repelled by a magnetic field.

Paramagnetic

Compounds that are attracted to a magnetic field.

Jahn-Teller (JT) Effect

a geometrical distortion of non-linear molecules or ions, such as the d orbitals take on the configuration of x2 -y2 highest in energy, followed by the z2 , then the zy and zx at a degenerate level, and the xy lying lowest in energy. The xy orbital falls in energy relative to before the distortion.

Π Donor Ligands

Pi bases, have filled pi orbitals about the M-L axis, and are lower in energy than the σ orbitals.

Π Acceptor Ligands

Pi acids, have empty pi orbitals available for occupation about the M-L acis.

X-ray Absorbance Spectroscopy (XAS)

Electrons are ejected from the core.

X-ray absorption near edge fine structure (XANES)

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