Transition Metals Flashcards
What block are transition metals?
d-block
Why do certain characteristics occur within transition metals?
Due to an incomplete d-sub level in their atoms or ions
What characteristic properties are associated with transition metals?
- complex formation
- formation of coloured ions
- variable oxidation states
- catalytic activity
What is a ligand?
A molecule or ion that forms a co-ordinate bond with a transition metal by donating a pair of electrons
Describe the complex that transition metals form?
A central metal atom or ion surrounded by ligands
What is the co-ordination number?
The number of co-ordinate bonds to a central atom or ion.
What is a lewis base?
Lone pair donor
What is a lewis acid?
Lone pair acceptor
Give examples of 3 monodentate ligands
H₂O, NH₃ and Cl-
Which monodentate ligands are uncharged?
H₂O and NH₃
Which transition metal undergoes incomplete substitution reactions?
Copper forms [Cu(NH₃)₄(H₂O)₂]²⁺
Why does Cl- form 4 co-ordinate bonds instead of 6?
Because it is larger than the other uncharged ligands
Give three factors that cause ΔE to change
- Co-ordination number
- Ligand
- Oxidation state
Give two examples of bidentate ligands
- ethane-1,2-diamine
- ethanedioate
What are bidentate ligands?
Form two co-ordinate bonds and donate two electron pairs
Give two examples of multidentate ligands?
- EDTA⁴⁻
- Haemoglobin
What are the uses of EDTA⁴⁻?
- an antidote for metal poisoning, removes it from blood
- anticoagulant, removes Ca²⁺ and prevents blood from clotting
What is chelation?
Entropically driven reaction because there are moles on the right side of the arrow. The enthalpy change is close to 0 because you are breaking and forming the same number of bonds.
Which transition metal ion is found in haem?
Fe²⁺
What co-ordinate bonds are formed in haemoglobin?
- 4 to a porphyrin rig
- 5th to globin protein
- 6th to oxygen (or carbon monoxide)
What is the common shape that transition metal complexes form?
Octahedral
What types of isomerism that transition metal complexes form and when does this happen?
- Cis-trans: monodentate ligands
- Optical: bidentate ligands
What shape do transition metal complexes form with Cl-?
Tetrahedral
What type of shape shows cis-trans isomerism?
Square planar
What silver complex is used in Tollens reagent?
[Ag(NH₃)₂]⁺
Why are transition metals coloured?
Colour arises when some wavelengths of light of visible light are absorbed and the remaining wavelengths are reflected.
d electrons are excited from ground level when light is absorbed
What is the equation for the energy change when d electrons are excited?
∆E = hν = hc/λ
Outline an experiment to determine the concentration of a solution with a colorimeter.
- Add a ligand to intesify the colour
- Make up solutions of known concentrations
- Measure absorption
- Plot results on a graph and draw a curve of best fit
- Measure unknown absorption and compare on calibration curve
What are the colours of vanadium species in different oxidation states?
V²⁺= purple V³⁺= green VO²⁺= blue VO₂⁺= yellow
What can be used to reduce species of vanadium?
Zinc with sulphuric acid. Hydrochloric acid can’t be used because it could be oxidised to toxic chlorine gas
Redox titration equation of Fe²⁺ and MnO₄⁻
5Fe²⁺ + MnO₄⁻ + 8H⁺ –> Mn²⁺ + 4H₂O + 5Fe³⁺
Redrox titration equation of MnO₄⁻ and C₂O₄²⁻
2MnO₄⁻ +16H⁺ + 5C₂O₄²⁻ –> 2Mn²⁺ + 8H₂O + 10CO₂
Explain why iron(III) ions are more acidic than iron(II) ions
- [Fe(H₂O)₆]³⁺ → [Fe(H₂O)₅(OH)]²⁺ + H⁺
- Fe³⁺ ion has higher charge density than Fe²⁺
- weakens O–H bond
