2.5(P1) Transition Metals

Question 1

What is the definition of transition metals?

Answer 1

One that forms at least one stable ion with a part-full d sub level of electrons

Question 2

What are some properties of transition metals?

Answer 2

Hard/strong metals
Good conductors of heat electricity
Low chemical reactivity
High melting and boiling points
All are in the d block, not all d block are transition metals
When ions form they lose an electron in the s sub-level not d

Question 3

What two elements don’t fit the pattern of electron configuration?

Answer 3

Chromium

Copper

Question 4

What are the 4 main characteristics of transition metals?

Answer 4

Form complexes
Form coloured compounds
Have variable oxidation states
Have catalytic activity

This all results from their electronic structure

Question 5

What is different about transition metals to normal metals?

Answer 5

The form co-ordinate bonds instead of a weak electrostatic force like most metals

This is due to a partially filled 3d sub-level

Question 6

What are complexes?

Answer 6

A transition metal surrounded by ligands

Which are co-ordinately bonded to the (ion) in the middle

Question 7

How do you draw a complex?

Answer 7

The metal (ion) in the middle
Surrounded but the ligand (eg water)
Arrows between the two to show the co-ordinate bond
All contained within square brackets
The charge of the metal ion if it has one on the outside (because water is neutral so it isn’t changed)

Question 8

What is the co-ordinate number?

Answer 8

The number of co-ordinate bonds

Question 9

Can you have a complex without a charge?

Answer 9

Yes

It’s just a complex
Not a complex ion

Question 10

What is a ligand?

Answer 10

A ligand is a species that can donate one or more lone pairs to form a co-ordinate bond to the transition metal

Question 11

How is the ligand water involved in complexes?

Answer 11

Only one of it’s two lone pairs are used in co-ordinate bonding
As one of the lone pairs faces the opposite direction

Question 12

Why can transition metals form complexes?

Answer 12

They have a partially filled 3d sublevel

Question 13

What are the names for complexes with a co-ordination number of:
6?
4 (x2)?
2?

Answer 13

6 = octahedral 
4 = tetrahedral or square planar 
2 = linear

Question 14

What is a unidentate ligand?

Answer 14

Forms a single co-ordinate bond no matter how many lone pairs it has

Question 15

What should you be careful of when working out the charge on a complex?

Answer 15

If the ligand also has a charge which should be taken into account with the metal (ion)

I.e chloride and cyanide

Question 16

What is a bidentate ligand?

Answer 16

They have lone pairs on different atoms so can ‘bend’ round to form 2 co-ordinate bonds

Question 17

Examples of a unidentate ligand?

Answer 17

H2O
Cl-
NH3
CN-

Question 18

Give some examples of a bidentate ligand?

Answer 18

1,2 - diaminoethane(no charge)

Ethanedioate ion (2-)
Which comes from having 2 carboxyl groups on each end with the hydrogens removed

1,2 - dihydroxybenzene (no charge)

Question 19

Why must you be careful with bidentate ligands?

Answer 19

It could be forming 6 co-ordinate bonds however this would only be from 3 ligands
As each bidentate ligand supplies 2 lone pairs

Question 20

What bidentate is abbreviated and what to?

Answer 20

1,2 - diaminoethane

Is abbreviated to

(en)

Question 21

What is a multidentate ligand?

Answer 21

They have more than one atom with a lone pair that they can donate

Question 22

Give an example of a multidentate ligand?

Answer 22

EDTA (4-)

22 lone pairs
Only 6 lone pairs are used

A lone pair from each of the 4 outer oxygens
A lone pair from the 2 nitrogens

Question 23

What is the chelate effect?

Answer 23

If you add EDTA to a solution of a transition metal salt, EDTA will replace all 6 water ligands in the aqua ion

2 reactants are replaced by 7 products therefore an increase in entropy moves the reaction to the right
Therefore polydentate ligands are favoured over monodentate ligands

Question 24

What are bridges?

Answer 24

A bidentate ligand can form a bridge between 2 metal ions (almost like a polymer)

‘Linking’

Question 25

Describe the prosthetic group haem?

Answer 25

Square planar

Carries oxygen

Question 26

Describe haemoglobin?

Answer 26

The oxygen it carries forms a temporary co-ordinate bond

CO - carbon monoxide can join instead of O2 forming a permeant bond

Question 27

What is Cisplatin?

Answer 27

Platinum with 2 chlorine ligands and 2 ammonia ligands (same ligand on the same side)

Square planar
Used to treat some types of cancer in chemotherapy

Z-platin

Question 28

What is significant about transplatin? Why?

Answer 28

Transplatin or E-platin
Doesn’t work in chemotherapy

As cisplatin has a higher melting point as in more soluble due to it being polar (ligands on the same side = more EN)

Question 29

What complexes do you draw if asked for:
Linear?
Tetrahedral?
Octehedral?

Answer 29

Linear: Ag(silver) with 2 ammonia ligands = 1+ complex
(Used in tollen’s reagent)

Tetrahedral: Co(cobalt) with 4 chlorine ligands attached = 2- complex

Octahedral: Fe(iron) with 6 water ligands attached = 2+ complex

Question 30

What do you draw if they want an octahedral shape using a bidentate ligand?

Answer 30

Co(cobalt) with 3 ethandioate ions = 4- complex

Question 31

Q) draw the possible octahedral complexes of CrCl3 where both Cl and H2O can act as ligands?

How would they react with silver nitrate?

Answer 31

CrCl3(H2O)3
CrCl2(H2O)4 (1+ charge) +Cl-
CrCl(H2O)5 (2+ charge) +2Cl-

First won’t react with silver nitrate as all chlorines are being used in co-ordinate bonds
Second will react to produce silver chloride
Third will also react to produce silver chloride (double the previous moles produced)