Transition metals

Question 1

What are d block transition metals

Answer 1

The d-block transition metals are metals with an incomplete d subshell in at least one of their ions.

Question 2

The filling of d orbitals follows what principal

Answer 2

The filling of the d orbitals follows the aufbau principle, with the exception of chromium and copper atoms.

Question 3

Why do chromium and copper atoms not follow the aufbau principal

Answer 3

These exceptions are due to the special stability associated with the d subshell being half- filled or completely filled.

Question 4

What happens to electrons when atoms from the first row of transition elements form ions

Answer 4

When atoms from the first row of the transition elements form ions, it is the 4s electrons that are lost first rather than the 3d electrons.

Question 5

When is a element said to be in a particular oxidation state

Answer 5

An element is said to be in a particular oxidation state when it has a specific oxidation number.

Question 6

How many states can a transition metal have in its compounds

Answer 6

A transition metal can have different oxidation states in its compounds.

Question 7

What colours are compounds of the same transition metal in different oxidation states

Answer 7

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

Question 8

Oxidation

Answer 8

Oxidation can be defined as an increase in oxidation number.

Question 9

Reduction

Answer 9

Reduction can be considered as a decrease in oxidation number.

Question 10

What can be used to determine whether ox or red has occurred in transition metals

Answer 10

Changes in oxidation number of transition metal ions can be used to determine whether oxidation or reduction has occurred.

Question 11

What is the difference in compounds containing Hugh oxidation states compared to low oxidation states

Answer 11

Compounds containing metals in high oxidation states are often oxidising agents, whereas compounds with metals in low oxidation states are often reducing agents.

Question 12

What are ligands

Answer 12

Ligands may be negative ions or molecules with non-bonding pairs of electrons that they donate to the central metal atom or ion, forming dative covalent bonds.

Question 13

Ligands can be classified as:

Answer 13

monodentate, bidentate, up to hexadentate.

Question 14

How can you deduce the ligand classification

Answer 14

It is possible to deduce the ligand classification from a formula or structure of the ligand or complex.

Question 15

What is the coordination number

Answer 15

The total number of bonds from the ligands to the central transition metal is known as the coordination number.

Question 16

What happens to d orbitals in a complex of a transition metal

Answer 16

In a complex of a transition metal, the d orbitals are no longer degenerate.

Question 17

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

Answer 17

Splitting of d orbitals to higher and lower energies occurs when the electrons present in approaching ligands cause the electrons in the orbitals lying along the axes to be repelled.

Question 18

What are strong field ligands

Answer 18

Ligands that cause a large difference in energy between subsets of d orbitals are strong field ligands.

Question 19

What are weak field ligands

Answer 19

Weak field ligands cause a small energy difference.

Question 20

What is the spectrochemical series

Answer 20

Ligands can be placed in an order of their ability to split d orbitals. This is called the spectrochemical series.

Question 21

When is light absorbed

Answer 21

Light is absorbed when electrons in a lower energy d orbital are promoted to a d orbital of higher energy.

Question 22

What happens if light of one colour is absorbed

Answer 22

If light of one colour is absorbed, then the complementary colour will be observed.

Question 23

What else can transition metals act as

Answer 23

Transition metals and their compounds can act as catalysts.

Question 24

What is the state of heterogenous catalysts

Answer 24

Heterogeneous catalysts are in a different state to the reactants.

Question 25

What state are homogenous catalysts in

Answer 25

Homogeneous catalysts are in the same state as the reactants.

Question 26

Homogenous catalysts

Answer 26

Homogeneous catalysis can be explained in terms of changing oxidation states with the formation of intermediate complexes.

Question 27

What does the presence of unpaired d electrons or infilled d orbitals allow

Answer 27

The presence of unpaired d electrons or unfilled d orbitals is thought to allow activated complexes to from. This can provide reaction pathways with lower energies compared to the uncatalysed reaction

Question 28

Which ions are more stable

Answer 28

Half fill or full filled sub shell stability more stable

Question 29

Monodentate ligand examples and charges

Answer 29

Chlorido - Cl- Ammine NH3 - neutral ligand Aqua OH2 - neutral ligand Cyanido - CN- Nitrito - NO2-

Question 30

What is an explanation of the spectrochemcial series

Answer 30

- changing the ligand of a transition metal changes the repulsion in d electrons /orbitals this changes the level of splitting therefore changing the energy absorbed when d electrons and promoted to higher levels changing the wavelength of light that’s absorbed.

Question 31

When a complex is colourless /least colourful

Answer 31

No d electrons in the subshell or D electron is full

Question 32

Naming transition metal complexes

Answer 32

1. The formula of the complex ion should be enclosed within square brackets, The metal Symbol is written first, then the ligands in alphabetical order. Eg. (Fe(NHs)-(OH2412* 2. The name of the complex ion or molecule consists of two parts written as one word. The ligands are named first and the central metal ion second 3. The ligand name is preceded by a prefix showing the number of ligands (di. tri, etc). If the ligand is a negative ion the name of which ends in -ide. the ending changes to o e.g. Chloride, CI becomes chlorido, cyanide, CN becomes cyanido. If the ligand is a negative ion which ends in -ite, the final 'e' changes to 'o', e.g. nitrite, NO2. changes to nitrito. 4.The metal name is followed by its oxidation state in Roman numerals in brackets. If the complex is an anion (negative ion), 'ate' is added to the name of the metal, sometimes the name ending of the metal is dropped. Sometimes the Latin name is used, e.g. ferrate not ironate, cuprate not copperate.

Question 33

The oxidation number can be determined by the following:

Answer 33

- uncombined elements have an oxidation number of 0 - ions containing single atoms have an oxidation number that is the same as the charge on the ion - in most of its compounds, oxygen has an oxidation number of −2 (except in peroxides) - in most of its compounds, hydrogen has an oxidation number of +1(except in hydrides) - the sum of all the oxidation numbers of all the atoms in a neutral compound must add up to zero - the sum of all the oxidation numbers of all the atoms in a polyatomic ion must be equal to the charge on the ion

Question 34

Ligands can be placed in a spectrochemical series based on their ability to split d orbitals.

Answer 34

I-< Br -< CI-< F- < H20 < NH3 < CN-

Question 35

Exceptions to aufbau rule chromium

Answer 35

Chromium - aufbau principal Actual configuration Reason 1s? 2s? 2p6 3s? 3р6 3d4 4s2. 1s? 25? 2p6 35? 3p6 3d5 4s1. Half-filled 3d5 preferred to full 4s2

Question 36

Exceptions to aufbau rule - copper

Answer 36

Copper - aufbau Actual configuration Reason 1s2 2s2 2p6 3s23р6 3d94s2. 1s? 2s? 2p6 35? 3p6 3d10 4s1. Full 3d10 preferred to full 4s2

Question 37

What is the coordination number EDTA hexaaquacopper (II) tetrachloridocuprate(ll)

Answer 37

• EDTA has a co-ordination number of 6 • hexaaquacopper(Il) [Cu(OH2)6]2+ has a co-ordination number of 6 as the central Cu2+ ion is surrounded by 6 water molecules • tetrachloridocuprate(Il)[CuCIa]2-has a co-ordination number of 4 as the central C2?+ ion is surrounded by 4 negative chloride ions