Transition Metals Flashcards
lewis acid vs b-l acid
L = accepts e pairs B-L = donates hydrogens
ions
lose electrons form 4S first
normally 4s 3d but becomes 3d
colour
3d orbitals split
light energy absorbed = energy gap
e’s jump from ground to excited state
reflected light is seen - energy in visible range
coordinate bond
shared pair of electrons from one atom in a covalent bond
transition metal definition
1 or more ions formed with incomplete D sub shells
ligands bond
COVALENT not ionic
tm complex
central metal ion surrounded by coordinately bonded ligands
ligand
atom/molecule that donates electron pair
Sc
Cr
Cu
Zn
not a TM
4s1 3d5
4s1 3d10
not a TM
chemical properties
variable oxidation states
coloured compounds
catalysts
complex ions
catalysts
iron - haber process
vanadium oxide - contact process
rhodium - catalytic converters
unidentate
bidentate
multidentate
ligand that forms 1 CO-B
forms 2
more than one CO-B
unidentate ligand
h20 - lone pairs v close together
:Cl- - chloride ion
NH3
:CN- - cyanide
bidentate ligand
en = ethane-1,2,diamine :NH2
ethanedioate (2-) - C2O4 (one O double bond on C) :O-
multidentate ligand
EDTA 4- = 6 CO-B’s
incr entropy so incr stability
TM dissolved in water
aqua ion
6 H2O ligands
octahedral shape
TM ion shape w/ 2 ligands
linear
TM ion shape w/ 4 ligands
tetrahedal
but platin is square planar -> cisplatin = anti-cancer drug that stop replication of cancerous cells but suppresses immune system
TM ion shape w/ 6 ligands
octahedral
stereoisomerism
cis/trans
optical isomerism in octahedral w/ 2 or more bidentate ligands…… using CIS bc unsymmetrical + non superimposable mirror images
:Cl- vs NH3 and H2O
4 coordinate bonds vs 6
since Cl is large
factors of TM ion colour
coordination number
ligands
oxidation states
colour energy
energy needed to jump = energy gap ΔE
ΔE = h v ( plancks constant x freq of light absorbed)
ΔE = h c / λ ( pc x speed of light / wavelength)
if no 3d electrons or 3d sub level is full…
no electron jump
no energy absorbed
compound = white or colourless cuz all light reflected
colorimetry/spectroscopy - why
calculate conc of complex by measuring how much light absorbed
colour intensity ∝ conc
colorimetry/spectroscopy - steps
white light shone through filter
filter only lets colour of light absorbed pass
passes through sample to colorimeter
add on ligand to intensify colour if only TM sol
variable oxidation states
have partially filled d-orbitals, so can lose 4s and 3d electrons
vanadium and ox states
VO2 + - 5+ - yellow
VO 2+ - 4+ - blue
V 3+ - 3+ - green
V 2+ - 2+ - violet
vanadium oxide + zinc
half eq VO2 (+) + 2H(+) + e- ----> VO (2+) + H2O VO (2+) + 2H(+) + e- ----> V(3+) + H2O V3(+) + e- ----> V(2+) 3e-'s all together
Zn —-> ZN (2+) + 2e-
3:2 ratio so… V’s x2 and Zn x3
overall:
8H(+) + 3Zn + 2VO2 (+) —-> 3Zn (2+) + 4H2O + 2V(2+)
tollen’s reagent
[Ag(NH3)2]+
Ag = (1+)
Ag(+) + e- —> Ag
when added to aldehyde - Ag+ is reduced
aldehyde oxidises to carboxylic acid = silver mirror
reducing/oxidising agents
reducing agent SO is oxidised SO loses electrons
Fe(2+) –> Fe(3+) + e-
oxidising agent SO is reduced SO gains electrons
Cl2 + 2e- –> 2Cl(-)
redox
balance O’s with H2O
balance H’s with H+
balance charges with e-
ratio of e-‘s
MnO4(-) –> Mn(2+)
deep purple to pink
5e- + 8H(+) + MnO4(-) –> Mn(2+) + 4H2O
Cr2O7(2-) –> Cr(3+)
orange to green
6e- + 14H(+) + Cr2O7(2-) –> 2Cr(3+) + 7H2O
aqua metal ions in acidic/alkaline conditions
acidic - reduced
alkaline - oxidised
oxylate ions
C2O4(2-) –> 2CO2 + 2e-
iron ions and manganate ions
Fe(2+) –> Fe(3+) + e-
5e- + 8H(+) + MnO4(-) –> Mn(2+) + 4H2O
e’s are 1:5
5Fe(2+) + MnO4(-) + 8H(+) –> 5Fe(3+) + Mn(2+) + 4H2O
equilibrium displaced
no. reactant molecules smaller and no. product molecules bigger
disorder increase
entropy increase
iron importance
needed for haemoglobin
define homogenous vs heterogenous
same state/phase vs different phase to the reactants
without catalyst, activation energy is high
negative ions which repel
catalyst properties
has variable oxidation states
ea lowers due to oppositely charged ions attracting
catalyst can be reduced and oxidised back
heterogenous catalyst
reactants adsorb to its active site
bonds weaken
desorb
contact process
V2O5 catalyst
SO2 + 1/2 O2 —> SO3
STEP 1: SO2 + V2O5 → SO3 + V2O4
STEP 2: V2O4 + ½O2 → V2O5
iodine clock
S2O8(2-) + 2 I(-) → 2SO4 (2-) + I2
v high ae since -ve repel
SO iron ii catalyst
S2O8 (2-) + 2Fe (2+) → 2Fe(3+) + 2SO4 (2-)
2Fe(3+) + 2I(-) → 2Fe(2+) + I2
auto catalysis
Mn2+ = catalyst
5e- + 8H(+) + MnO4(-) –> Mn(2+) + 4H2O
C2O4(2-) –> 2CO2 + 2e-
2:5 ratio SO
5C2O4(2-) + 16H(+) + 2MnO4(-) –> 2Mn(2+) + 8H2O + 10CO2
Mn(2+) —> Mn(3+) + e-
STEP 1: MnO4(-) + 4Mn(2+) + 8H(+) → 4H2O + 5Mn(3+)
STEP 2: 2Mn3(+) + C2O4(2-) → 2CO2 + 2Mn(2+)
autocatalysis
product of a reaction is also a catalyst for that reaction
impurities in heterogenous reaction
block active sites/deactivates catalyst
graph
reaction is slow/shallow grad as conc of reactant used
faster/gradient incr as catalyst forms
fe cr2o7
1:6
