Inorganic Chem:Midterm 2 review

chapters 5,6,9, 10 (Molecular Orbital theory, Acid-Base theories, Coordination complexes, Crystal field theory.)

When calculating bond order, what do the calculated values tell you?

Bond Order = ½ ((Electrons in Bonding MOs) - (Electrons in Antibonding MOs))

Higher values indicate stronger bonds.

• Bond Order = 1: Single bond.

• Bond Order = 2: Double bond.

• Bond Order = 0: The molecule is unstable and won't exist (like He₂)

• Fractions: Unlike Lewis structures, MO theory allows for bond orders of 0.5, 1.5, 2.5, etc.

What atoms in the first period of the periodic table experience s-p mixing?

N and to the left experience s-p mixing

Paramagnetic means:

The molecule has unpaired electrons. It will be attracted to a magnetic field

Diamagnetic means:

All electrons are paired. It will be slightly repelled by a magnetic field (e.g., N2)

Arrhenius Model

acids give hydrogen ions in aqueous solution and bases give hydroxide in aqueous solution

Bronsted-Lowry Model

acids are hydrogen ion donors and bases are hydrogen ion acceptors

Lewis Model

acids are electron pair acceptors and base are electron-pair donors

What are the limitations of the Arrhenius Acid-Base Model

1)of limited use in non-aqueous solvents or the gas phase where dissociation doesn’t occur

2) fails to capture analogous reactivity of substances that don’t dissociate into H+ or OH- example: NH3

Hard Lewis acids:

Hard Lewis acids are typically small, highly charged metal ions that preferentially interact with hard bases. Hard acids stabilize negative charges more effectively, enhancing the stability of the resulting complexes.

Soft lewis acid:

Soft Lewis acids are larger, less charged metal ions that prefer to interact with soft bases. They stabilize positive charges and are often covalently bonded to softer donor atoms.

hard lewis base

A hard Lewis base is a species with a small size and high electronegativity that readily donates electron pairs to hard Lewis acids.

"All-in-One" Rule:

All Arrhenius acids are Brønsted-Lowry acids, and all Brønsted-Lowry acids are Lewis acids. The reverse is not always true.

What is the conservation of Orbitals?

If you start with n atomic orbitals (AOS), you must end with n molecular orbitals (MOs)

Bond order and length relationship:

High B.O. = Shorter bond length and higher bond strength (dissociation energy)

why does s-p mixing occur?

In light homonuclear diatomic (Li₂ through N₂), the energy gap between the 2s and 2p orbitals is small. This causes them to "mix," which pushes the sigma_g(2s) lower and the sigma_g(2p) higher in energy.

HOMO: highest occupied molecular orbital

The molecular orbital that contains the highest energy electrons in a molecule. It plays a crucial role in determining the chemical properties and reactivity of the molecule. Acts as a Lewis base (electron donor)

LUMO: lowest unoccupied molecular orbital

the first “empty” molecular orbital that can accept electrons. Acts like a Lewis Acid (electron acceptor)

Reduction formula

n= 1/h sum of [(number of operations in class)*(X_reducing) * (X_irreducible)

Assigning Central Atom symmetry

• s-orbital: Always matches the "totally symmetric" representation (e.g., A₁ or A₁g

• p-orbitals ($p_x, p_y, p_z$): Look for the rows containing x, y, or z.

• d-orbitals: Look for the rows containing xy, xz, yz, z², or x²-y²

The golden rule;

only orbitals of the same symmetry species can overlap to form MOs.

state the three definitions of the Acid-Base theories

Theory	Acid Definition	Base Definition	Example
Arrhenius	Increases (H+) in water	Increases [OH-] in water	HCl (acid) / NaOH (base)
Brønsted-Lowry	Proton (H+) Donor	Proton (H+)Acceptor	NH4+ (acid) / NH3 (base)
Lewis	Electron Pair Acceptor	Electron Pair Donor	BF3 (acid) / NH3 (base)

Hard/Soft Acid-Base (HSAB) Theory

Hard likes hard, and soft likes soft:

Hard Acids/Bases: Small, high charge (for ions), low polarizability

Soft Acids/Bases: Large, low charge, high polarizability

Solubility behavior:

Solubility: AgI (Soft-Soft) is very insoluble in water because the bond is very strong/covalent. LiF (Hard-Hard) is also quite stable.

Pearson’s Absolute Hardness (n)

A scale used to quantify the hardness or softness of acids and bases, determining their preference in acid-base reactions based on charge density and polarizability.

I = ionization energy of the molecules in eV approximately equal to E_HOMO

A = the electron affinity of the molecules in eV, approximately equal to -E_LUMO

Drago’s E-C approach

a method used to evaluate acid-base interactions based on their covalent and ionic characteristics, emphasizing the role of electronegativity and atomic size in determining acid-base strength.

-Delta H = E_A E_B + C_A C_B

what do the E and C values represent in Drago’s E-C approach?

• E parameters: Represent the Electrostatic (Hard) contribution.

• C parameters: Represent the Covalent (Soft) contribution.

Electronic effects

Inductive effects : Electron-withdrawing groups (like F or Cl) pull electron density away from the acidic site, making it easier for H⁺ to leave (increasing acidity) or making a Lewis acid more electron-hungry.

Resonance: If the conjugate base can spread its negative charge over several atoms via resonance, the original acid is much stronger (e.g., Phenol is more acidic than Ethanol).

Steric effects

Steric effects refer to the influence of the spatial arrangement of atoms in a molecule on its reactivity and stability. In acid-base chemistry, bulky groups can hinder interactions, affecting the strength of acids and bases.

metal-ligand adduct

Facial(fac)

Three identical ligands form one face of the octahedron (all 90° apart).

Meridional(mer)

Three identical ligands form a "T-shape" or a meridian (two are 180° apart).

Delta isomers

Isomers where ligands are arranged in a way that two pairs of identical ligands occupy positions on opposite sides of the coordination complex, resulting in a distinctly different optical activity.

Lambda isomers

Isomers where ligands are arranged in a way that two pairs of identical ligands occupy adjacent positions around the coordination complex, leading to a specific type of optical activity.

Determining chirality for an Octahedral:

Trans isomers are almost always achiral (they have a plane of symmetry).

• Cis isomers with bidentate ligands (like cis-[Co(en)₂Cl₂]⁺) are usually chiral.

• Tris-chelated complexes ([M(en)₃]ⁿ⁺) are always chiral.

Crystal Field Theory

The model treats ligands as negative point charges and the metal-ligand interaction as purely electrostatic(ionic)

Ligand Field Theory

The model an application of molecular orbital theory to transition metal complexes

Define Chelating ligands

Chelating ligands are molecules or ions that have two or more points of attachment to a metal ion, effectively 'grabbing' it to create a more stable complex. donate more than one pair of electrons to the metal atom

ligands with one point of attachment are called?

monodentate ligands (literally "one-tooth" ligands): donate one pair of electrons to the central metal atoms

name the three types of structural isomers

ionization, coordination, and linkage

name the two types of sterioisomers

geometric and optical isomers

Nomenclature for coordination complexes: what is inside the brackets

contains the coordination sphere, including the central metal and its ligands.

Nomenclature for coordination compunds steps:

1) name the ligand (alphabetically, regardless of charge or prefix)

2) places prefix (di-, tri-, tetra-, penta-, hexa-

3) name the central metal

4) determine the state of oxidation

name this coordination compound: K₃[Fe(CN)₆]

potassium hexacyanoferrate(III)

name this coordination compound: [Co(NH₃)₆]Cl₂

hexaamminecobalt(II) chloride

name this coordination compound: [Co(H₂O)₆]I₃

hexaaquacobalt(III) iodide

name this coordination compound: K₂[PtCl₄]

potassium tetrachloroplatinate(II)

name this coordination compound: K₄[PtCl₆]

potassium hexachloroplatinumate(II)

name this coordination compound: [Co(NH₃)₅Cl]Cl₂

pentaamminechlorocobalt(III) chloride