General Properties of Transition Metals (Booklet 1)

Question 1

What are the characteristics of transition metals ?

Answer 1

Complex formation
Formation of coloured ions
variable oxidation states
catalytic activity

Question 1

What is a transition metal ?

Answer 1

a d-block element that forms atleast one stable ion with an incomplete d-subshell

Question 2

What is a ligand ?

Answer 2

a molecule or anion which donates a lone pair of electrons to a central metal ion to form a coordinate bond

Question 3

What is a complex ?

Answer 3

a central metal atom or ion bonded to one or more ligands by coordinate bonds

Question 4

What is coordination number ?

Answer 4

the number of coordinate bonds to the central atom or ion

Question 5

How many coordinate bonds to monodentate ligands form ?

Answer 5

One

Question 6

What type of complexes do transition metals usually form with small ligands such as water?

Answer 6

octahedral

Question 7

What type of complexes do transition metals usually form with large ligands such as chloride ion?

Answer 7

tetrahedral

Question 8

What is a bidentate ligand ?

Answer 8

a ligand that has two atoms with a lone pair which can each form coordinate bonds with the central metal ion.

Question 9

What are two examples of bidentate ligands ?

Answer 9

Ethane-1,2-diamine
Ethanedioate ion

Question 10

What is a multidentate ligand ?

Answer 10

a ligand that can form two or more coordinate bonds to a transition metal ion from different atoms on the same ligand.

Question 11

What is an example of a multidentate ligand

Answer 11

EDTA4-

Question 12

What can EDTA be described as ? HINT: it forms 6 coordinate bonds

Answer 12

a hexadentate ligand

Question 13

Describe the haem complex

Answer 13

The central Fe 2+ ion has a coordination number of 6
Haem is an iron(II) complex with a multidentate ligand.
Four of the coordination sites are used by a ring structure known as porphyrin

Question 14

How does haemoglobin allow oxygen to be transported around the blood

Answer 14

oxygen forms a coordinate bond to Fe(II) in haemoglobin
This is weakly bonded as O2 is not a very good ligand and so it can be readily given upto cells.

Question 15

Why is carbon monoxide deadly ?

Answer 15

CO can also act as a ligand and forms a stable complex with haemoglobin

It can displace O2 from the complex and prevent O2 from being transported to cells.

Question 16

What are stereoisomers ?

Answer 16

species with the same structural formula but a different arrangement of atoms in space.

Question 17

What are characteristics of a cis isomer ?

Answer 17

they have two of the same ligand at 90 degrees to each other (i.e next to each other)

Question 18

What characteristics do trans isomers have ?

Answer 18

they have two of the same ligand at 180 degrees to eachother

Question 19

There are two isomers cis-platin and trans-platin which one acts as an anti cancer drug ?

Answer 19

Cis-Platin

Question 20

How does Cis-Platin work ?

Answer 20

Binds to the DNA of fast growing cancer cells
This prevents DNA from unwinding and replicating
and so prevents cell division

Question 21

What are the disadvantages of using Cis platin ?

Answer 21

it has serious medical side effects

Question 22

How can the risks from using cis platin be minimised ?

Answer 22

by using small amounts and targeting the application.

Question 23

What are optical isomers ?

Answer 23

Species with the same structural formula but a different arrangement of atoms in space existing as none superimposable mirror images

Question 24

What do optical isomers do ?

Answer 24

rotate the plane of polarised light

Question 25

A mixture containing equal concentrations of each isomer is known as what ?

Answer 25

a racemic mixture

Question 26

Why does a racemic mixture have no effect on the plane of polarised light ?

Answer 26

the rotations of the isomers would cancel out

Question 27

What is Ligand substitution ?

Answer 27

a reaction in which one ligand coordinately bonded to a central metal atom or ion is replaced by another.

Question 28

What is complete substitution ?

Answer 28

when all the ligands in a complex are replaced by a different ligand

Question 29

What is incomplete substitution ?

Answer 29

when only some ligands in the complex are replaced.

Question 30

Why might the enthalpy change in a ligand substitution reaction be zero?

Answer 30

If the number of bonds broken is equal to the number of bonds formed
The bonds broken also have similar enthalpy to the bonds made.

Question 31

what does it mean if there is a positive entropy change ?

Answer 31

AS is positive
There is an increase in moles so an increase in disorder.

Question 32

What does it mean if there is a negative entropy change ?

Answer 32

AS is negative
There has been a decrease in moles ( particles) so a decrease in disorder.

Question 33

What is the chelate effect ?

Answer 33

The substitution of monodentate ligands by a bi-or multidentate ligand to form a more stable complex.

Question 34

What is an example of the chelate effect ? state the reaction

Answer 34

Aqueous copper 2+ ions reacting with EDTA4-

Question 35

What are the requirements for optical isomerism ?

Answer 35

A complex with three Bidentate ligands

A complex with 2 bidentate and 2 monodentate

Question 36

Why are six water ligands replaced by only four chloride ions ?

Answer 36

cl- is too big
Therefore only four chloride ions can fit around the central metal atom
Also the negative charges on the ligands repel each other