Transition metals

Question 1

What is a transition metal?

Answer 1

An element with an incomplete d sub-shell in one of its common ions.

Question 2

What is special about how Cu fills?

Answer 2

[Ar] 4s1 3d10

Question 3

What is special about how Cr fills?

Answer 3

[Ar] 4s1 3d5

Question 4

What are properties of transition metals?

Answer 4

Variable oxidation states, catalytic action, coloured compounds, forms complexes. High b.p., ductile, malleable

Question 5

What is a ligand?

Answer 5

Particle with lone pair of electrons that bonds to metals by co-ordinate bond

Question 6

What is a co-ordination number?

Answer 6

Number of co-ordinate bonds from ligands to metal ion

Question 7

What are unidentate, bidentate and multidentate ligands?

Answer 7

Uni - one bond
Bi - two bonds to a metal ion
Multi - more than two

Question 8

What is Haemaglobin?

Answer 8

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

Question 9

What is Pt(NH3)2Cl2? What are its isomer?

Answer 9

Cis platin and trans platin. Cis platin is an effective anti-cancer drug with the same molecules next to each other.

Question 10

What is a complex ion?

Answer 10

A central metal ion surrounded by ligands.

Question 11

What is the process of swapping ligands in a complex?

Answer 11

Ligand substitution (usually water being swapped out)

Question 12

What is the chelate effect?

Answer 12

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.

Question 13

What are ligands that form many bonds called?

Answer 13

Chelating agents and are very good at bonding to a metal and hard to remove. E.g. EDTA4- forming 6 co-ordinate bonds

Question 14

Why are complexes coloured?

Answer 14

-Five d orbitals have different energy. -Electrons absorb light and are excited. -The non absorbed light is seen.

Question 15

Why are Zn2+, Cu+ and Sc3+ not coloured?

Answer 15

Have empty or full d sub shells so no promotion of e’s possible

Question 16

What 4 things can affect colour of complexes?

Answer 16

Metal type, metal oxidation state, ligand type and co-ordination number. These change energy gap size

Question 17

What colours are vanadium’s oxidation states?

Answer 17

+5 yellow, +4 blue, +3 green, +2 purple

Question 18

In general how does PH affect oxidation state of transition metals?

Answer 18

Easier to oxidise transition metal in alkaline conditions and reduce in acidic.

Question 19

What is needed to reduce vanadium?

Answer 19

Acidic conditions and zinc reducing agent.

Question 20

What happens in the reduction of Cr2O7(VI)2-

Answer 20

In acidic conditions with zinc chromium is reduced from Orange +6, to Cr3+ green, to Cr2+ blue.

Question 21

How do you oxidise Cr3+ to Cr2O72-?

Answer 21

In acidic conditions with hydrogen peroxide.

Question 22

What is the equation to change between the two Chromium(VI)?

Answer 22

2CrO4 2- + 2H+ Cr2O7 2- + H2O