Transition Metals Flashcards
D block
Elements where d shell level is the highest energy sub shell containing electrons
Cr electron structure
[Ar] 4s 1 3d 5
Gives additional stability to atom half filled sub shell
Cu electron structure
[Ar]4s1 3d10 full d orbital giving additional stability
Transition elements
D block elements that form at least one ion with a partially filled d orbital
Sc and zinc aren’t (Sc loses 3e-) (Zn forms a full d orbital)
Properties of trans metals and compounds
Form compounds which transition element has different oxidation states
Form coloured compounds
Act as catalysts
Complex ions
One of most important properties of d block element
When one or more negatively charged ions bond to a central metal ion molecules are called ligands
Ligand
A molecule or ion that donates a pair of electrons to form a coordinate bond
Coordinate bond
When one of the bonded atoms provide both of the electron for the shared pair
Coordination number
Number of coordinate bonds attached to the central metal ion
Monodentate ligands
Donate one pair of electrons to a central metal ion
Shapes of complex ions
Octahedral
Tetrahedral
Square planar
Octahedral
The most common shape
6 coordinate bonds
Tetrahedral
4 coordinate bonds
109.5 degrees
CuCl4 for example
Square planar
4 coordinate bonds occurs in ions with 8 d electrons
90 degree bond angles
Cis trans in complex ions
Most common in square planar complexes
Cis= 2 adjacent identical groups 90
Trans = 2 identical opp side 180
Monodentate ligands in cos trans
Octahedral
90 degrees away = cis
180 degrees away = trans opposite side
Bidentate ligands cis trans
Bidentate ligands adjacent = cis
Bidentate ligands are opp = trans
Optical isomerism
Non superimposable mirror images of each other
Only possible with 3 Bidentate ligands 2 Bidentate + 2 mono
1 hexadentate ligand
Ligand substitution
When one ligand is replaced by a different / another ligand in a complex ion
Ligand sub with nh3 and [Cu(H20)6]^2+
Pale blue to dark blue solution
4 H20 ligands replaced by 4 NH3 ligands
Cu(OH)2 pp forms and then dissolved in excess ammonia
Ligand substitution with Cl- (conc HCl)
Pale blue to yellow solution
6 H2O replaced by 4 Cl-
Octahedral -> square planar
Cl- ions are larger than H2O so fewer can fit round Cu 2+
Reactions of Cr ions
Cr(H2O)6 ^3+ violet
Ammonia - Cr(OH)3 (grey/green) formed dissolves in excess ammonia -> purple
Ligand sub in haemoglobin
Oxygen bonds to Fe2+ of haem group
Co2 also bonds to Fe2+
Carbon monoxide binds to form carboxyhaemoglonin which binds v strongly so ligand sun doesn’t occur
Oxygen cannot be picked up
Precipitation reactions
When 2 aq sol containing ions react together to form an insoluble ionic solid
Transition metals and precipitation
+ aq sodium hydroxide and aq ammonia
Form pp
Some may dissolve further to form complex ions
Addition of NaOH ( insoluble)
Cu2+ blue sop to form insoluble blue pp Cu(OH)2
Fe2+ pale green sol form green pp Fe(OH)2 turns brown at surface
Fe3+ pale yellow to form orange brown pp Fe(OH)3
Mn2+ pale pink to light brown pp Mn(OH)2
Addition of NaOH ( soluble)
Cr3+ violet forms grey green pp
Soluble in excess forming dark green solution -> [Cr(OH)6]^3-
Further addition of ammonia
Cu(OH)2 -> [Cu(NH3)4(H2O)2]2+ blue pp to deep blue sol
Cr(OH)3 -> [Cr(NH3)6]^3+ green pp to purple solution
Fe2+,Fe3+ and Mn2+ react with excess ammonia forming pp of Fe(OH)2 for example
Iodine thiosulphate equation
2S2O3 2- + I2 => 2I- + S4O6 2-
Starch black blue to colourless
S2O3 2-
Thiosulphate ions are oxidised lose 2e-
2 per I2
1:1 thiosulphate ions to iodide ions I-
I2
Iodine is reduced
Gains 2e-
Thiosulphate ratios
1:1 ratio = Cu 2+ : S2O3 2-
S2O3 2- : I-
2:1 ratio= S2O3 2- : I2
