LO's - transition metals

Question 1

Define a d-block transition metal

Answer 1

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

Question 2

Explain why chromium and copper are exceptions to the aufbau principle of orbital filling

Answer 2

This is due to the special stability of filled or half filled d subshells. Chromium is [Ar]3d5 4s1 rather than [Ar]3d4 4s2 . Copper is [Ar]3d10 4s1

Question 3

Which electrons are lost first (4s or 3d) when atoms in the first row of transition metals form ions?

Answer 3

4s

Question 4

SKILL) Determine the oxidation state of a transition metal using the set of oxidation number rules

Answer 4

.

Question 5

Explain oxidation and reduction in terms of oxidation number

Answer 5

Oxidation is an increase in oxidation number. Reduction is a decrease in oxidation number.

Question 6

State the link between oxidation number and oxidising agent/reducing agent

Answer 6

Compounds containing metals in high oxidation state are often oxidising agents (able to accept electrons) and low oxidation state metals are often reducing agents (able to donate electrons)

Question 7

Define the term ‘ligand’

Answer 7

Negative ions or molecules with non-bonding pairs of electrons that they can donate to the central metal atom or ion, forming dative covalent bonds

Question 8

Explain the terms ‘monodentate’, ‘bidentate’ and ‘polydentate’

Answer 8

Relating to the number of pairs of electrons donate. Monodentate - ligand donates one pair of electron. bi = 2, poly = many

Question 9

Define the term ‘coordination number’

Answer 9

The total number of bonds from the ligands to the central transition metal

Question 10

(SKILL) Write names and formulae for transition metal complexes using the IUPAC rules

Answer 10

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Question 11

Explain why the d orbitals in transition metals complexes are no longer degenerate

Answer 11

Electrons in approaching ligands cause the electrons in the orbitals lying along the axes to be repelled.

Question 12

What is meant by the terms ‘strong field ligand’ and ‘weak field ligand’

Answer 12

Strong field ligands are ligands which cause a large difference in energy between the d orbitals and weak field ligand cause a small difference in energy between d orbitals (ie. d orbitals are split less)

Question 13

What is the spectrochemical series?

Answer 13

Ligands can be placed in order of their ability to split d orbitals - this is the spectrochemical series.

Question 14

Explain why colours of transition metal complexes can be explained by d orbital splitting?

Answer 14

Light is absorbed when electron in a lower energy d orbital are promoted to a d orbital of higher energy. If light of one colour is absorbed, the complementary colour will be observed

Question 15

Explain why transition metals and their complexes act as catalyst?

Answer 15

Unpaired d electrons or unfilled d orbitals allows intermediate complexes to occur. This can provide reaction pathways with lower activation energies compared to the uncatalysed reaction.
The fact that TM complexes can have variable oxidation states is an important factor.

Question 16

Explain what homogeneous catalysis means

Answer 16

Homogeneous catalysts are in the same state as the reactants

Question 17

Explain what heterogeneous catalysis means

Answer 17

Heterogeneous catalysts are in a different state to the reactants.