Transition Metals

Question 1

Properties of transition elements

Answer 1

Atoms or stable ions with incomplete d subshell
Form complexes
Variable oxidation states
Catalytic activity
Form coloured ions

Question 2

Ligand

Answer 2

Have atleast one lonenpair of electrons to form coordinate bond to central metal atoms empty orbital
Monodentate- one coordinate bond ( Cl- OH- CN-)
Bidentate- two coordinate bonds ( oxalate C2O4,2- 1,2-diaminoethane H2NCH2CH2NH2 )
Multidentate- many coordinate bonds (EDTA4-)

Question 3

Coordination number

Answer 3

Number of coordinate bonds to metal atom

Question 4

Chelates

Answer 4

Complexes formed from multidentate ligand
Bound more tightly due to chelate effect
Metal atom is fully surrounded

Question 5

Ligand substitution with no change in coordination number

Answer 5

Smaller ligand which are similar in size and uncharged
E.g water and ammonia
Bidentate replacing monodentate or other bidentate

Question 6

Ligand substitution with a change in coordination number

Answer 6

Larger charged ligands (Cl-) reduces coordination number to 4
Larger so less will fit, negative charges also repel each other

Question 7

Substitution feasibility

Answer 7

Enthalpy change- mainly negligible as same type of coordination bonds and number of coordination bonds are broken and made.
Will be a change where coordination number changes, if more broken than made its exothermic if more made than broken it’s Endothermic
Entropy change- determines if reaction is feasible
Feasible if number of molecules increases

Question 8

Chelate effect

Answer 8

Budentate and multidentate ligands increase number of molecules in solution so increases entropy so complex formed is more stable

Question 9

Coordination number of 6

Answer 9

Octagedral shape
Small monodentate ligands- E-Z isomerism
Bidentate ligands- optical isomerism

Question 10

Coordination number 4

Answer 10

Tetrahedral complex (Cl-)
Square planar complex (no overall charge eg cisplatin)- E-Z isomerism

Question 11

Cisplatin

Answer 11

Only cis isomer (Z) shows anti cancer activity
Forms links between bases in DNA in tumour cell
Stops tumour growth
Expensive due to Pt content
Side effects: death, organ damage, hair loss

Question 12

Coordination number 2

Answer 12

H3N-Ag-NH3
Used in tollens reagant

Question 13

Formation of coloured ions

Answer 13

Copper(ii) - blue
Iron(ii)- pale green
Cobalt(ii)- pink

Question 14

Colours in transition metal

Answer 14

D sublevel must be partially filled
D sub shell split into two sets with an energy difference
Visible light absorbed and excited electrons to higher energy level
Complimentary colour reflected and observed

Question 15

What effects the colour of a complex

Answer 15

Oxidation states of central atom
Coordination number
Type of ligand
Shape of complex
All of these cause different splitting of the d subshell causing different colour to be reflected

Question 16

Calculations of energy, frequency and wavelength

Answer 16

E= Hv
C= Hh
E- energy difference
H- planck constant
h- wavelength
C- speed of light

Question 17

Hexaaqua ion colours with NaOH

Answer 17

Cu(ii)- blue solution to blue ppt
Fe(ii)- green solution to green ppt
Fe(iii)- orange solution to brown precipitate
Al(iii)- colourless solutionnto white ppt redissolves in excess

Question 18

Hexaaqua ion reactions with ammonia

Answer 18

Cu(ii)- blue solution to blue ppt redissolves in excess for deep blue solution
Fe(ii)- green solution to green ppt
Fe(iii)- orange solution to brown precipitate
Al(iii)- colourless solutionnto white ppt

Question 19

Hexaaqua ion reactions with sodium carbonate

Answer 19

Cu(ii)- blue solution to green ppt
Fe(ii)- pale green solution to green ppt
Fe(iii)- orange solution to brown ppt with bubbles
Al(iii)- colourless solution to white ppt with bubbles