# Transition Metals and Coordination Chemistry

## Vocabulary

### actinide series

f-block elements in period 7 of the periodic table, which consists of elements actinium (Ac) through lawrencium (Lr)

### bidentate ligand

ligand in a coordination complex that donates two pairs of electrons to the central metal atom or ion

### chelate

coordination complex formed between a central metal atom or ion and chelating ligands, which are ions or molecules that bond to it with more than one atom

### cis configuration

geometric arrangement in which two identical substituents are on the same side of the central part of a molecule or an ion

### coordination complex

central metal atom or ion surrounded by ligands, as well as bonded ions if the central part has an overall charge

### coordination number

number of atoms bound to the single central metal center in a coordination complex

### coordination sphere

part of a coordination complex consisting of the central metal atom or ion and all ligands surrounding it

### crystal field splitting energy

energy difference between the higher energy $e_g$ (${d_{{z^2}}}$and ${d_{{x^2}-{y^2}}}$) and lower energy $t_{2g}$ (${d_{xy}}$, ${d_{yz}}$, and ${d_{xz}}$) symmetric orbitals

### crystal field theory

electrostatic model that is used to describe and predict energy differences between nd orbital sets in transition metal complexes

### d-block element

element with one or more valence electrons in a d orbital

### f-block element

element with 4f or 5f electrons in its valence shell

### geometric isomer

one of two or more molecules that have the same molecular formula and bond structure but differ in the positions of substituents around a rigid part of the molecule

### high-spin complexes

complex in which electrons fill higher orbitals singly and the pairing energy is large relative to the crystal field splitting energy

### ionization isomer

one of two forms of a coordination complex that differ only in which of two species is a ligand and which is outside the coordination sphere

### isomer

one of two or more molecules that share the same chemical formula but have different arrangements of atoms

### lanthanide series

f-block elements in period 6 of the periodic table, which consists of elements lanthanum (La) to lutetium (Lu)

### ligand

ion or molecule that bonds to a central metal atom or ion as part of a coordination complex

one of two or more coordination complexes that differ in how a ligand is bonded to the central metal atom or ion

### low-spin complexes

complex in which electrons preferentially pair in lower-energy orbitals and the pairing energy is small relative to the crystal field splitting energy

### monodentate ligand

ligand in a coordination complex that donates a single pair of electrons to the central metal atom or ion

### optical isomer

one of a pair of mirror-image molecules that are not identical and cannot be superimposed

### pairing energy (P)

energy required for two electrons to occupy a single orbital

### polydentate ligand

ligand in a coordination complex that donates three or more pairs of electrons to the central metal atom or ion

### rare earth element

one of 15 lanthanides and 2 transition metals that have similar chemical properties and are commonly found together in nature

### smelting

technique by which an elemental metal is extracted from its ore through heating and melting

### spectrochemical series

list of ligands ordered according to their ability to induce crystal field splitting for a common metal center

### superconductor

material that can conduct electric current with almost zero resistance when cooled to appropriate temperatures

### trans configuration

geometric arrangement in which two identical substituents are on opposite sides of the central part of a molecule or an ion

### transition metal

element in groups 3 through 12 of the periodic table