Transition metals

Question 1

What is a transition metal?

Answer 1

has an incomplete d-subshell either as an element or as one of its common ions

Question 2

What are the four characteristics of transition metals?

Answer 2

-can form complexes
-can form coloured ions
-have variable oxidation states
-catalytic activity

Question 3

Why is copper a transition metal?

Answer 3

-although the atom of copper does not have an incomplete d-subshell
-but Cu2+ does have an incomplete d-subshell

Question 4

Why is zinc not a transition metal?

Answer 4

neither zinc nor Zn2+ have an incomplete d-subshell

Question 5

What is the most common ion complex shape, bond angle, and coordination number?

Answer 5

octahedral, 90, 6

Question 6

How many monodentate ligands can form?

Answer 6

6 coordinate bonds to the central metal ion

Question 7

What is a complex ion?

Answer 7

consists of a central transition metal ion with ligands that are covalently bonded to it via coordinate bonds

Question 8

What is a ligand?

Answer 8

a species that can donate one or more pairs of electrons to the metal ion

Question 8

What are monodentate ligands?

Answer 8

form one co-ordinate bond to the central metal ion

Question 9

What are some monodentate ligands?

Answer 9

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

Question 10

What is a bidentate ligand?

Answer 10

form two co-ordinate bonds to the central metal ion

Question 11

What are some bidentate ligands?

Answer 11

1,2-diaminoethane (H2NCH2CH2NH2) , ethanedioate (C2O42-)

Question 12

What can you shorten 1,2-diaminoethane to?

Answer 12

en

Question 13

What are multidentate ligands?

Answer 13

form three or more co-ordinate bonds to the central metal atom

Question 14

What is an example of a multidentate ligand?

Answer 14

H2EDTA can form the anion EDTA4- which can form 6 bonds with the metal ion and completely surrounds it

Question 15

What are chelates?

Answer 15

the complexes formed when bidentate or multidentate ligands bond to a central metal ion

Question 16

Why are chelate complexes more stable?

Answer 16

their formation results in an increase of entropy/increase in disorder since more chemical species are formed - chelate effect

Question 17

Name some uses of EDTA?

Answer 17

-remove dangerous metal ions from blood - antidote to metal poisoning
-used in blood transfusions to remove calcium ions to stop clotting

Question 18

What is haem?

Answer 18

an iron(II) complex with a multidentate ligand, with atoms octahedrally around iron(II)

Question 19

How does haemoglobin transport oxygen around the body?

Answer 19

oxygen molecules form weak bonds with the iron(II)

Question 20

Why is carbon monoxide toxic?

Answer 20

it can replace oxygen co-ordinately bonded to Fe(II) in haemoglobin, as it forms a stronger bond - therefore reducing the oxygen-carrying capacity

Question 21

What are smaller ligands?

Answer 21

H2O, NH3

Question 22

What are larger ligands?

Answer 22

halide ions

Question 23

What shape of complex is more likely to form with larger ligands?

Answer 23

tetrahedral

Question 24

Why do fluoride ions not form tetrahedral coplexes?

Answer 24

the F- ions are smaller than Cl- ions

Question 25

What is a less common complex shapes?

Answer 25

square planar - 90degrees

Question 26

What is an example of a square planar shape?

Answer 26

cisplatin - Cl --> ... <--NH3 .........................Pt................ ................Cl --> ... <--NH3

Question 27

What is cisplatin and how does it work?

Answer 27

-an anti-cancer drug used in chemotherapy -works by preventing DNA replication in cancer cells -does a ligand-replacement reaction with DNA in which a co-ordinate bond is formed between platinum and a nitrogen atom on guanine -a second nitrogen from another guanine can replace the second chlorine too -causes the strands to kink and can't unwind properly

Question 28

What are the side effects of cisplatin?

Answer 28

-binds to healthy cells too -hearing loss -nausea -kidney damage

Question 29

Give an example of a linear complex

Answer 29

tollens reagent - [NH3 --> Ag <-- NH3]+ SILVER IONS AND COPPER(I) IONS TEND TO FORM LINEAR COMPLEXES

Question 30

Why are transition metal complexes coloured?

Answer 30

-they can absorb visible light, but only some -reflected light contains the frequencies that are not absorbed

Question 31

What can affect the colour of the transition metal ion?

Answer 31

-type of ligand -coordination number -oxidation state of the transition metal

Question 32

What is a d-d transition?

Answer 32

electrons in the lower 3d subshell absorb energy from visible and UV light radiation which excites/promotes them to the higher 3d subshell

Question 33

What dictates the frequency of visible light absorbed?

Answer 33

the ΔE between the 2 sets of 3d subshells

Question 34

When are more intense colours observed?

Answer 34

when the electron moves from a ligand orbital to a metal - charge transfer transitions

Question 35

How to calculate ΔE?

Answer 35

ΔE = hc/λ ΔE = hv h - plancks constant c - speed of light v - frequency λ - wavelength(m)

Question 36

Why do transition metals have variable oxidation states?

Answer 36

the 4s and 3d electrons are both available for bonding

Question 37

Apart from scandium (+3), what is the oxidation state of the first row of transition metals?

Answer 37

+2 - loss of 4s electrons. more stable as the increasing nuclear charge causes the 3d electrons to be held more tightly

Question 38

What is the oxidation state of manganese?

Answer 38

+7

Question 39

What is a property of the lower oxidation states?

Answer 39

-simple ions -said to be reducing

Question 40

What is a property of the higher oxidation states?

Answer 40

-found in complex ions/compounds with very electronegative elements like oxygen (CrO7 2-, VO2 +) -said to be oxidising