Transition Metals and Complex Formation

Vocabulary-style flashcards covering transition metal properties, electronic configurations, complex ion formation, isomerism, catalysis, and related chemical processes.

d-block elements

The elements from titanium to copper where electrons are being added to a $3d$ sub-level.

Transition element

An element that forms at least one stable ion with a part-full d-shell of electrons.

Scandium ($Sc$)

A d-block element that is NOT a transition metal because it only forms $Sc^{3+}$ ($3d^0$), which has an empty d-shell.

Zinc ($Zn$)

A d-block element that is NOT a transition metal because it only forms $Zn^{2+}$ ($3d^{10}$), which has a full d-shell.

Chromium ($Cr$) electronic configuration

$[Ar] 3d^5 4s^1$. It has a half-full d-sub-level which is believed to make the atom more stable.

Copper ($Cu$) electronic configuration

$[Ar] 3d^{10} 4s^1$. It has a full d-sub-level, providing stability similar to a noble gas.

Variable oxidation states

The ability of transition metals to have more than one oxidation state in their compounds, allowing them to participate in redox reactions.

Ligand

An ion or molecule with a lone pair of electrons that forms a co-ordinate bond with a transition metal ion.

Complex ion

A species formed when a transition metal ion is surrounded by ligands which are bonded to it by co-ordinate bonds.

Co-ordination number

The number of co-ordinate bonds formed between ligands and a central d-block metal ion.

Co-ordinate bond

A type of covalent bond (also known as a dative bond) where both electrons in the shared pair come from the same atom.

Aqua ions

Species formed when the salt of a transition metal dissolves in water, causing the metal ion to be surrounded by water ligands in an octahedral arrangement.

Multidentate ligands

Molecules or ions that have more than one atom with a lone pair of electrons capable of bonding to a transition metal ion.

Bidentate ligands

Ligands that can form two co-ordinate bonds per molecule, such as ethane-1,2-diamine ($en$) or the ethanedioate ion ($C_2O_4^{2-}$).

EDTA

Ethylenediaminetetracetate; a hexadentate ligand that uses lone pairs on four oxygen atoms and two nitrogen atoms to bond to a transition metal.

Chelate effect

The phenomenon where chelate complexes with polydentate ligands are favored over monodentate ligands due to an increase in entropy ($\triangle S$) when more particles are produced.

Haemoglobin

A molecule consisting of an $Fe^{2+}$ ion with a co-ordination number of six. Four sites are bound to a porphyrin tetradentate ligand (haem), one to globin, and the sixth to oxygen.

Tollens' reagent

A linear complex ion $[Ag(NH_3)_2]^+$ used to distinguish aldehydes (which reduce it to metallic silver) from ketones.

Cisplatin

A square planar geometrical isomer of platin where $Cl^-$ ligands are next to each other; it is used as a successful anti-cancer drug.

Optical isomers

Isomers that are non-superimposable mirror images of each other, capable of rotating the plane of polarised light; also described as chiral.

Planck's constant expression

$\triangle E = hv$, where $\triangle E$ is the energy gap between d-orbitals, $h$ is Planck's constant, and $v$ is the frequency of light absorbed.

Colorimetry

A technique using a light source and detector to measure the concentration of coloured transition metal solutions using absorbance and calibration graphs.

Heterogeneous catalyst

A catalyst that is in a different phase (e.g., solid) than the reactants (e.g., gases or liquids), where the reaction occurs on the solid surface.

Catalyst poisoning

The process where the surface of a heterogeneous catalyst becomes covered with unwanted impurities, reducing its efficiency.

Contact process

The industrial manufacture of sulfuric acid using vanadium(V) oxide ($V_2O_5$) as a catalyst to oxidise $SO_2$ to $SO_3$.

Homogeneous catalyst

A catalyst in the same phase as the reactants, which usually works by forming an intermediate species.

Autocatalysis

A type of catalysis where one of the products of a reaction acts as a catalyst for that same reaction.