Transition Metals (3.2.5)

Question 1

What is a transition metal?

Answer 1

An element that has an incomplete d sub-shell in either its atoms or one of its common ions

Question 2

Properties of transition metals

Answer 2

• Variable oxidation states
• Catalytic action
• Coloured compounds
• Formation of complexes

Question 3

What is a ligand?

Answer 3

A particle with a lone pair of electrons that bonds to metals by a dative/co-ordinate bond

Question 4

What is a complex?

Answer 4

A metal ion surrounded by co-ordinately bonded ligands

Question 5

What is the co-ordination number?

Answer 5

• The number of coordinate bonds from ligands to the metal ion
• (Harpoons)

Question 6

What is a Lewis base?

Answer 6

A lone pair donor (nucleophile)

Question 7

What is a Lewis acid?

Answer 7

A lone pair acceptor (electrophile)

Question 8

How many H2O ligands bond to a transition metal?

Answer 8

6

Question 9

How many NH3 ligands bond to a transition metal?

Answer 9

6

Question 10

How many Cl- ligands bond to a transition metal?

Answer 10

4

Question 11

How many ligands can Ag bond to?

Answer 11

2 (always linear)

Question 12

LEWIS BASE or LEWIS ACID

1) Ligands
2) Metal ion

Answer 12

1) Lewis Base –> donates a pair of electrons

2) Lewis Acid –> accepts lone pairs

Question 13

What is the co-ordination number of a linear complex?

Answer 13

2

Question 14

What is the co-ordination number of a square planar complex?

Answer 14

4

Question 15

What is the co-ordination number of a tetrahedral complex?

Answer 15

4

Question 16

What is the co-ordination number of an octahedral complex?

Answer 16

6

Question 17

Examples of linear complexes

Answer 17

• Ag+ complexes

- e.g. [Ag(NH3)2]+ (Tollen’s reagent)

Question 18

Examples of square planar complexes

Answer 18

• Pt 2+ & Ni 2+ complexes

- e.g. [PtCl4]2- (cisplatin)

Question 19

Examples of tetrahedral complexes

Answer 19

• Larger ligands (too big to fit 6)
• Cl-
• e.g. [CuCl4]2-

Question 20

Examples of octahedral complexes

Answer 20

• Most complexes with small ligands (so 6 can fit)
• H2O, NH3 etc
• e.g. [Cu(H2O)6]2+ (blue)

Question 21

What is a unidentate ligand?

Answer 21

A ligand that forms one co-ordinate bond to a metal ion

Question 22

Example of unidentate ligands

Answer 22

Cl-, OH-, CN-, H2O, NH3

Question 23

What is a bidentate ligand?

Answer 23

A ligand that forms two co-ordinate bonds to a metal ion

Question 24

Example of bidentate ligand

Answer 24

> 1,2-diaminoethane (en)

> ethanedioate ion (C2O4 2-)

Question 25

What is a multidentate ligand?

Answer 25

A ligand that forms more than two co-ordinate bonds to a metal ion

Question 26

Example of a multidentate ligand

Answer 26

> EDTA 4- (6 bonds, octopus) | > Porphyrin (4 bonds)

Question 27

What is Haemoglobin made up of?

Answer 27

- Globular protein, made up of four Fe2- centres - each with a porphyrin ligand taking up four of the six co-ordination sites - One site is bonded to the structure - One site is left to take up oxygen as a ligand - Oxygen is not a great ligand, so can fall off easily to be used for respiration. Cyanide and (CN-) and carbon monoxide (CO) are better ligands, so stick to haemoglobin better than oxygen and prevent transport of oxygen (asphyxia)

Question 28

What shapes of molecules can display cis-trans isomerism?

Answer 28

- Square Planar | - Octahedral

Question 29

Example of cis-trans isomerism?

Answer 29

- Cisplatin (effective anti-cancer drug) | - Transplatin (no effect on cancer)

Question 30

What shape of molecule can optical isomerism display in?

Answer 30

- Octahedral (only bidentate ligands) | - Mirror Plane reflection

Question 31

What is ligand substitution?

Answer 31

A reaction where one ligand is replaced by another

Question 32

What happens to the co-ordination number if H2O's are replaced by NH3's?

Answer 32

- As NH3 and H2O are similar sizes, there is no change in co-ordination number - [Co(H2O)6]2+ + 6NH3 --> [Co(NH3)6]2+ + 6H2O

Question 33

What happens to the co-ordination number if the substitution is by a different sized ligand?

Answer 33

- The co-ordination number may change - e.g., Cl- ligands are significantly bigger than H2O or NH3, so only 4 can fit around a central ion - Therefore the co-ord number changes (6-->4) - [Co(H2O)6]2+ + 4Cl- --> [CoCl4]2- + 6H2O - Charge stays same, overall 2-

Question 34

What is the Chelate effect?