2.5 Transition Metal Flashcards
What defines a transition metal in terms of electron configuration?
A transition metal has an incomplete d sub-level in atoms or ions.
Why is zinc not considered a transition metal?
Because Zn²⁺ has a complete d-orbital (3d¹⁰), and does not exhibit typical transition metal properties.
What are typical characteristics of transition metals?
Complex formation, formation of coloured ions, variable oxidation states, and catalytic activity.
What is a complex in transition metal chemistry?
A central metal ion surrounded by ligands bonded through co-ordinate (dative covalent) bonds.
What is a ligand?
An atom, ion or molecule that donates a lone pair of electrons to form a co-ordinate bond with a central metal ion.
What determines the co-ordination number of a complex?
The number of co-ordinate bonds formed to the central metal ion.
What are examples of monodentate ligands?
H₂O, NH₃, and Cl⁻.
What are examples of bidentate ligands?
Ethane-1,2-diamine (NH₂CH₂CH₂NH₂) and ethanedioate ion (C₂O₄²⁻).
What is a multidentate ligand example?
EDTA⁴⁻, which can form six coordinate bonds per ligand.
What is the chelate effect?
The increased stability when monodentate ligands are replaced with bidentate or multidentate ligands due to a positive entropy change.
What shapes can complex ions form?
Octahedral (e.g., [Cu(H₂O)₆]²⁺), tetrahedral (e.g., [CoCl₄]²⁻), square planar (e.g., cisplatin), linear (e.g., [Ag(NH₃)₂]⁺).
What types of isomerism can complex ions show?
Cis-trans isomerism and optical isomerism.
What causes colour in transition metal complexes?
Electronic transitions between d orbitals that absorb visible light; the remaining transmitted light gives the complex its colour.
What factors can change the colour of a transition metal complex?
Changes in oxidation state, co-ordination number, or the type of ligand.
What equation links energy difference and frequency of absorbed light?
ΔE = hv or ΔE = hc/λ, where h is Planck’s constant and c is the speed of light.
Why is sulfuric acid used in manganate titrations?
It provides sufficient H⁺ ions without interfering in the redox reaction. HCl and HNO₃ are not suitable due to side reactions.
Why do manganate titrations need heating when oxalate is involved?
Because the initial reaction between MnO₄⁻ and C₂O₄²⁻ is slow due to repulsion between negative ions.
What is a heterogeneous catalyst?
A catalyst in a different phase than the reactants, often a solid where the reaction happens on the surface.
How do transition metals act as heterogeneous catalysts?
By providing active sites where reactants are adsorbed, weakening bonds and increasing reaction rate.
What is an example of homogeneous catalysis by a transition metal?
Fe²⁺ catalysing the reaction between S₂O₈²⁻ and I⁻.
What is autocatalysis?
A reaction where one of the products acts as a catalyst, e.g., Mn²⁺ in the reaction between MnO₄⁻ and C₂O₄²⁻.
What precipitates are formed when halide ions react with AgNO₃?
Cl⁻ = white (AgCl), Br⁻ = cream (AgBr), I⁻ = pale yellow (AgI).
How can Ag halide precipitates be differentiated using ammonia?
AgCl dissolves in dilute NH₃, AgBr dissolves in concentrated NH₃, AgI does not dissolve.
