1c- Transition metals

Question 1

What is a transition metal?

Answer 1

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

Question 2

The filling of d orbitals follows the aufbau principle with the exception of which two atoms?

Answer 2

Chromium and copper

Question 3

Why do the d orbitals in chromium and copper atoms not fill up following the aufbau principle?

Answer 3

Due to special stability associated with the d subshell being half-filled or completely filled

Question 4

When atoms from the first row of transition metals form ions, which electrons are lost?

Answer 4

4s electrons are lost first rather than the 3d electrons

Question 5

What do oxidation and reduction reactions involve?

Answer 5

The transfer of electrons

Question 6

How are oxidation numbers always written?

Answer 6

Sign first then number, e.g. +2 or -3

Question 7

What oxidation number do uncombined elements have?

Answer 7

Zero

Question 8

What is the oxidation number of an ion containing single atoms?

Answer 8

The oxidation number is the same as the charge on the ion

Question 9

In most of its compounds what is the oxidation number of oxygen?

Answer 9

-2

Question 10

In most of its compounds what is the oxidation number of hydrogen?

Answer 10

+1

Question 11

What must the sum of all the oxidation numbers of all the atoms in a neutral compound add up to?

Answer 11

Zero

Question 12

What must the sum of all the oxidation numbers of all the atoms in a polyatomic ion be equal to?

Answer 12

The charge on the ion

Question 13

Compounds of the same transition metal can have different colours, why is this?

Answer 13

Different oxidation states of the transition metal (a change in oxidation number usually means a change of colour)

Question 14

What can oxidation be defined as?

Answer 14

An increase in oxidation number

Question 15

What can reduction be defined as?

Answer 15

A decrease in oxidation number

Question 16

What can changes in oxidation number be used to determine?

Answer 16

Whether oxidation or reduction has occured

Question 17

Compounds containing metals in high oxidation states are often what?

Answer 17

Oxidising agents

Question 18

Compounds containing metals in low oxidation states are often what?

Answer 18

Reducing agents

Question 19

What is a ligand?

Answer 19

A molecule, ion or atom which contains at least one non-bonded pair of electrons

Question 20

What can a ligand do?

Answer 20

Donate their lone pair of electrons to the central metal atom or ion, forming a dative covalent bond (coordinate bond)

Question 21

How can ligands be classified and what do these classifications mean?

Answer 21

• monodentate (1-toothed) = can form one coordinate bond
• bidentate (2-toothed) = can form two coordinate bonds
• hexadentate (6-toothed) = can form six coordinate bonds

Question 22

What is the coordination number and what does it determine?

Answer 22

The total number of bonds from the ligands to the metal center, this determines shape

Question 23

What are the four rules when naming metal complexes?

Answer 23

1. number and name of ligands is given first
2. name of metal then oxidation number in brackets (roman numeral)
3. if complex is positive or neutral, name of metal doesn’t change
4. if complex is negative, ending changes to -ate

Question 24

How do ligands always appear?

Answer 24

In square brackets

Question 25

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

Answer 25

Degenerate

Question 26

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

Answer 26

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

Question 27

Ligands which cause a large difference in energy between subsets of d orbitals are known as what?

Answer 27

Strong field ligands

Question 28

Ligands which cause a small energy difference between subsets of d orbitals are known as what?

Answer 28

Weak field ligands

Question 29

Ligands can be placed in an order of their ability to split d orbitals. What is this called?

Answer 29

The spectrochemical series

Question 30

How can the colours of many transition metal complexes be explained?

Answer 30

In terms of d-d transitions

Question 31

What happens when electrons in a lower energy d orbital are promoted to a d orbital of higher energy?

Answer 31

Light is absorbed

Question 32

If light of one colour is absorbed, what colour will be observed?

Answer 32

The complementary colour

Question 33

When do electrons transition to higher energy levels?

Answer 33

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

Question 34

What can transition metals and their compounds act as?

Answer 34

Catalysts

Question 35

How can heterogeneous catalysts be described?

Answer 35

They are in a different state to the reactants

Question 36

What can heterogeneous catalysts be explained in terms of?

Answer 36

The formation of activated complexes and the adsorption of reactive molecules onto active sites

Question 37

How can homogeneous catalysts be described?

Answer 37

They are in the same state as the reactants

Question 38

What can homogeneous catalysts be explained in terms of?

Answer 38

Changing oxidation states with the formation of intermediate complexes