3.2.5 Transition Metals

Question 1

What is a transition metal?

Answer 1

forms one or more stable ions which have partially filled d subshell

Question 2

Why is Zn not a transition metal?

Answer 2

Zn only forms a Zn2+ ion that has a complete d subshell and so does not meet the criteria of a partially filled d subshell.

Question 3

Why is Sc not a transition metal?

Answer 3

Sc most stable ion is Sc3+, which has an empty d subshell and therefore is not a transition metal

Question 4

What are the properties of transition metals?

Answer 4

. Variable oxidation states
. Form complex ions
. Form coloured compounds
. Behave as catalyst

Question 5

Why do transition metals show variable oxidation numbers in compounds?

Answer 5

the energy to remove electrons from the 4s and 3d orbitals is very similar; hence multiple electrons can be removed
(we use roman numerals to indicate different oxidation states)

Question 6

What is a complex?

Answer 6

metal atom or ion surrounded by ligands

Question 7

What is a ligand?

Answer 7

an atom, ion or molecule which can donate a lone electron pair that bonds to metals by a coordinate bond

Question 8

What is a coordination number?

Answer 8

the number of coordinate bonds (dative covalent) formed by a central metal ion.

Question 9

What type of catalyst can transition metals act as?

Answer 9

Heterogeneous catalyst - different phase from reactants
Homogeneous catalyst - same phase as reactants

Question 10

Why can transition metals catalyse reactions?

Answer 10

Most transition metals have multiple stable oxidation states

Question 11

NCS PP TM L1 Catalysis slide 9 - rest not complete

Question 12

What is a monodentate ligand?

Answer 12

can form only one dative bond to the central metal ion

Question 13

Examples of monodentate ligands:

Answer 13

Water H2O
Ammonia NH3
Chloride Cl-
Cyanide CN-
OH-

Question 14

What is a bidentate ligand?

Answer 14

can donate 2 pairs of lone pairs of electrons and can each form 2 dative bonds to the central metal ion

Question 15

Examples of bidentate ligands:

Answer 15

. en H2NCH2CH2NH2 (1,2-diaminoethane)
. ox C2O42- (ethanedioate)

Question 16

What is a multidentate ligand?

Answer 16

can form more than two dative bonds

Question 17

Examples of multidentate:

Answer 17

EDTA4- hexadentate

Question 18

How to work out oxidation state of a transition metal?

Answer 18

total charge of complex - sum of all charges of ligands

Question 19

How do you work out the overall charge of a complex?

Answer 19

sum of the charge on the central on the central metal ion and the charges on each of the ligands

Question 20

What angle is linear and coordination number?

Answer 20

180
2

Question 21

What angle is tetrahedral and coordination number?

Answer 21

109.5
4

Question 22

What is haemoglobin?

Answer 22

A globular protein that contains four Fe2+ centres, each with a porphyria ligand taking up four of the six coordinate bonds. The other two bonds is the rest of the globin and an O2 or H2O

Question 23

Why does oxygen come off and when?

Answer 23

Not a good ligand

When needed to transfer cells for respiration

Question 24

What are better ligands than O2?

Answer 24

Cyanide ions (CN-) and carbon monoxide (CO)

Question 25

Why is CN- and CO toxic?

Answer 25

Prevent the transfer of oxygen

Question 26

When does cis-trans isomerism occur?

Answer 26

In octahedral and square planar complexes - where there are 2 ligands of one type different to the other ligands

Question 27

When does optical isomerism occur?

Answer 27

In octahedral complex with 3 bidentate ligands

Question 28

Explain one risk associated with the use of cisplatin as an anticancer drug.

Answer 28

Kills healthy cells and causes damage (side effect hair loss) May attach to DNA in normal cells

Question 29

What is ligand substitution?

Answer 29

Reaction where 1 ligand is replaced by another