Transition Metals Flashcards

Active recall practice for configurations, complex shapes, ligand substitution, colours, and catalysis mechanisms.

General Properties & Configurations: read all 5 questions and answers

Define transition metal.
A d-block element that forms at least one stable ion with a partially filled d subshell.
Write the full electron configuration of a copper (Cu) atom and a Cu²⁺ ion.
Cu: 1s²2s²2p⁶3s²3p⁶3d¹⁰4s¹; Cu²⁺: 1s²2s²2p⁶3s²3p⁶3d⁹ (the 4s electron is lost first).
Why are Scandium and Zinc classified as d-block elements but NOT transition metals?
Scandium forms only Sc³⁺ which has an empty d subshell (3d⁰); Zinc forms only Zn²⁺ which has a completely filled d subshell (3d¹⁰).
State the four characteristic properties of transition metals.
Variable oxidation states, formation of coloured ions, catalytic activity, and formation of complexes.
Why do transition metals show variable oxidation states?
The energy levels of the 3d and 4s subshells are very close, so different numbers of electrons can be lost with similar energy inputs.

Complex Shapes & Isomerism: read all 5 questions and answers

Define ligand.
An atom, ion, or molecule that donates a lone pair of electrons to a central metal ion to form a coordinate bond.
Give an example of a monodentate, a bidentate, and a multidentate ligand.
Monodentate: H₂O (or NH₃ / Cl⁻); Bidentate: 1,2-diaminoethane (en) (or C₂O₄²⁻); Multidentate: EDTA⁴⁻.
State the coordination number and shape of the complex [CuCl₄]²⁻.
Coordination number is 4; shape is tetrahedral.
What is cisplatin, and what is its shape and medical use?
Cisplatin is cis-[Pt(NH₃)₂Cl₂]; its shape is square planar; it is used as an anticancer drug.
Under what conditions can an octahedral complex display optical isomerism?
When it contains two or more bidentate ligands (such as [Co(en)₃]³⁺), forming non-superimposable mirror images.

Ligand Substitution & Colour: read all 5 questions and answers

Describe the pale blue copper complex in water, and the change in coordination number when excess concentrated HCl is added.
Pale blue [Cu(H₂O)₆]²⁺ is octahedral (coord number 6); adding HCl forms yellow-green [CuCl₄]²⁻ which is tetrahedral (coord number 4) due to large Cl⁻ ligand size.
Explain the chelate effect in terms of entropy.
Substituting monodentate ligands with bidentate or multidentate ligands increases the number of particles in solution, leading to a positive entropy change (ΔS>0) and highly stable complexes.
Explain why transition metal complexes are coloured.
Ligands split the d orbitals into two energy levels. Electrons absorb specific frequencies of visible light to be promoted to the higher level. The remaining unabsorbed light is transmitted as the complementary colour.
State the equation showing the relationship between light energy absorbed, frequency, and wavelength.
\(\Delta E = h\nu = \frac{hc}{\lambda}\) (where \(h\) is Planck's constant, ν is frequency, \(c\) is speed of light, and λ is wavelength).
Why are Sc³⁺ and Zn²⁺ complexes colourless?
Sc³⁺ has no d-electrons (3d⁰) and Zn²⁺ has a completely full d subshell (3d¹⁰), so no d-d transitions of electrons can occur.

Catalysis Mechanisms: read all 5 questions and answers

Define homogeneous and heterogeneous catalysts.
Homogeneous: catalyst in the same phase as reactants; Heterogeneous: catalyst in a different phase from reactants.
Describe the steps involved in heterogeneous catalysis.
Reactants are adsorbed onto active sites on the catalyst surface; bonds in reactants are weakened, leading to reaction; products are desorbed.
How does catalyst poisoning occur?
Impurities adsorb strongly and irreversibly to the active sites on the catalyst surface, blocking reactants from binding and reducing efficiency.
Write the two equations showing how Fe²⁺ acts as a homogeneous catalyst in the reaction between S₂O₈²⁻ and I⁻.
S₂O₈²⁻ + 2Fe²⁺ → 2SO₄²⁻ + 2Fe³⁺; then 2Fe³⁺ + 2I⁻ → 2Fe²⁺ + I₂.
What is autocatalysis, and which ion acts as the autocatalyst in the MnO₄⁻ / C₂O₄²⁻ reaction?
A reaction where one of the products acts as a catalyst for the reaction; Mn²⁺ ions act as the autocatalyst.