1.3 Transition metals

Question 1

Describe the d block transition metals

Answer 1

metals with an incomplete d subshell in at least one of their ions

Question 2

What principle does the filling of d orbitals follow?

Answer 2

aufbau principle
-with the exception of chromium and copper atoms

Question 3

Why do the d subshells of chromium and copper not follow the aufbau principle?

Answer 3

due to a special stability associated with the d subshell being half filled or completely filler

Question 4

What happens when an atom from the first row of transition metals form ions?

Answer 4

it is the 4s electrons that are lost first rather then the 3d electrons

Question 5

How can the oxidation number be determined?

Answer 5

• uncombined elements = 0
• single atom ions = same as the charge
• oxygen = -2
• hydrogen = +1
• neutral compound = all atoms must add up to 0
• polyatomic ion = equal the charge on the ion

Question 6

What can a transition metal have?

Answer 6

different oxidation states in its compound

Question 7

Explain colour changes in transition metals

Answer 7

Compounds of the same transition metal in different oxidation states may have different colours

Question 8

What is oxidation?

Answer 8

an increase in oxidation number

Question 9

What is reduction?

Answer 9

a decrease in oxidation number

Question 10

What can changes in oxidation number of transition metals be used for?

Answer 10

to determine weather oxidation or reduction has occurred

Question 11

What are compounds with metals in high oxidation states often?

Answer 11

Oxidising agents

Question 12

What are compounds with metals in low oxidation states often?

Answer 12

Reducing agents

Question 13

What are ligands?

Answer 13

• negative ions
• or molecules with non-bonding pairs of electrons
  -that they donate to a central metal ion
• forming dative covalent bonds

Question 14

What can ligands be classed as?

Answer 14

• monodentate
• bidentate
• up to hexadentate

Question 15

What is the coordination number?

Answer 15

the total number of bonds from the ligands to the central metal atom

Question 16

Names and formulae can be written according to IUPAC rules for complexes containing what?

Answer 16

• Central metals that obey the normal IUPAC rules
• Copper (cuprate) and iron (ferrate)
• Ligands including water, ammonia, halogens , cyanide, hydroxide and oxalate

Question 17

In a complex of a transition metal, what are the d orbitals no longer?

Answer 17

degenerate

Question 18

When does the splitting of d orbitals to higher and lower energies occur?

Answer 18

When the electrons present in approaching ligands cause the electrons in the orbitals lying along the axes to be repelled

Question 19

What are strong field ligands?

Answer 19

Ligands that cause a large difference in energy between subsets of d orbitals.

Question 20

What are weal field ligands?

Answer 20

Cause a small energy difference between subsets of d orbitals

Question 21

What is the spectrochemical series?

Answer 21

Ligands can be placed in order of their ability to split d orbitals

Question 22

How can colours of many transition metal complexes be explained?

Answer 22

In terms of d-d transitions

Question 23

When is light absorbed?

Answer 23

When electrons in a lower energy d orbital are promoted to a d orbital of higher energy

Question 24

What is shown when light of one colour is absorbed?

Answer 24

the complementary colour will be shown

Question 25

When do electrons transition to higher energy levels?

Answer 25

When energy corresponding to the ultraviolet or visible regions of the electromagnetic spectrum is absorbed

Question 26

What do transition metals and their compounds act as?

Answer 26

catalysts

Question 27

What are heterogeneous catalysts?

Answer 27

Heterogeneous catalysts are in a different state from the reactants

Question 28

Explain heterogeneous catalysts

Answer 28

• Can be explained in terms of the formation of activated complexes and absorption of reactive molecules onto active sites
• unpaired d electrons or unfilled d orbitals it is thought to allow activated complexes to form
• this can provide reaction pathways with lower activation energies compared to the uncatalysed reaction

Question 29

What are homogeneous catalysts?

Answer 29

Homogeneous catalysts are in the same state as the reactants

Question 30

Explain homogeneous catalysts?

Answer 30

• they can be explained in terms of changing oxidation states with the formation of the intermediate complexes