Transition metals GapFill

Transition metals are d-block elements that have, or form ions with, partially filled d subshells. In the case of the first-row transition metals, this is the  2d1d4d3d subshell.

In a transition metal complex, a central metal atom/ion is surrounded by ligands. Ligands are molecules or ions that can donate a lone pair to form a  conjugatecooperativecompoundcoordinate (dative covalent) bond. The number of these bonds made to the transition metal is called the  bondligandelectroncoordination number, while the number of lone pairs donated by a single ligand is called its   multiplicitydispositionorderdenticity. Complexes in which at least one ligand forms multiple bonds to the transition metal are called   hypoligatesmultiplexeschelatescingulates. The most common shapes for transition metal complexes are octahedral, square planar, linear and   trigonal planarT-shapedtetrahedralicosahedral.

Reactions in which one ligand is replaced by another are called ligand   alterationisomerisationsubstitutionelimination reactions. The feasibility of these reactions depends on the balance between ΔH, the change in enthalpy involved in the reaction, and ΔS, the change in  lattice energyentropyionisation energyGibbs free energy involved in the reaction.

Due to their variable oxidation states, transition metals and their compounds are often used as catalysts. Catalysts come in two types: heterogeneous, which are in a different phase to the reactants, and   idiogeneousequigeneousmonogeneoushomogeneous, which are in the same phase as the reactants. Heterogenous catalysis relies on the adsorption of reactant molecules into   liveactivefunctionalhot sites on the catalyst's surface.