Transition metals Flashcards
What is a transition metal?
An element with an incomplete d sub-shell in one of its common ions.
What is special about how Cu fills?
[Ar] 4s1 3d10
What is special about how Cr fills?
[Ar] 4s1 3d5
What are properties of transition metals?
Variable oxidation states, catalytic action, coloured compounds, forms complexes. High b.p., ductile, malleable
What is a ligand?
Particle with lone pair of electrons that bonds to metals by co-ordinate bond
What is a co-ordination number?
Number of co-ordinate bonds from ligands to metal ion
What are unidentate, bidentate and multidentate ligands?
Uni - one bond
Bi - two bonds to a metal ion
Multi - more than two
What is Haemaglobin?
A protein that contains four Fe2+ centres. With sites for oxygen to bond to. Oxygen is a bad ligand so comes off the iron easily for respiration. CO is better ligand and prevents Oxygen bonding
What is Pt(NH3)2Cl2? What are its isomer?
Cis platin and trans platin. Cis platin is an effective anti-cancer drug with the same molecules next to each other.
What is a complex ion?
A central metal ion surrounded by ligands.
What is the process of swapping ligands in a complex?
Ligand substitution (usually water being swapped out)
What is the chelate effect?
Swapping ligands out to form more co-ordinate bonds. This is feasible as there is an increase in entropy as overall number of aq molecules increases.
What are ligands that form many bonds called?
Chelating agents and are very good at bonding to a metal and hard to remove. E.g. EDTA4- forming 6 co-ordinate bonds
Why are complexes coloured?
-Five d orbitals have different energy. -Electrons absorb light and are excited. -The non absorbed light is seen.
Why are Zn2+, Cu+ and Sc3+ not coloured?
Have empty or full d sub shells so no promotion of e’s possible
What 4 things can affect colour of complexes?
Metal type, metal oxidation state, ligand type and co-ordination number. These change energy gap size
What colours are vanadium’s oxidation states?
+5 yellow, +4 blue, +3 green, +2 purple
In general how does PH affect oxidation state of transition metals?
Easier to oxidise transition metal in alkaline conditions and reduce in acidic.
What is needed to reduce vanadium?
Acidic conditions and zinc reducing agent.
What happens in the reduction of Cr2O7(VI)2-
In acidic conditions with zinc chromium is reduced from Orange +6, to Cr3+ green, to Cr2+ blue.
How do you oxidise Cr3+ to Cr2O72-?
In acidic conditions with hydrogen peroxide.
What is the equation to change between the two Chromium(VI)?
2CrO4 2- + 2H+ Cr2O7 2- + H2O
