3.4 - D Block Transition metals Flashcards
Transition metal?
metal with a partially filled D orbital
Orbitals of transition metals?
Ti to Zn all with an Ar core
what are the only exceptions?
copper + chromium as there is only a small difference between the energy of 3d and 4s
more energy is required to pair up the electrons to create a half filled D orbital and a fully filled D orbital
electron configuration for Fe
4S2 3D6
Electron configuration for Fe2+
4S03D6
Electron configuration for Fe3+
4S03D5
Where are electrons lost from first?
4S orbital first
Oxidation states for transition metals?
Sc?
+3 - common and only 1
Ti
+3 and + 4
+1 and +2
V?
+ 2+3+4,+5
+1
Cr?
+3 and +6
+1, +2,+4, and +5
Mn?
+2,+3+4,+6,+7
+1,+5
Fe?
+2, +3
+1,+4+5,+6
C?
+2,+3
+1,+4,+5,+6
Ni?
+2
+1,+3,+4
Cu?
+1,+2
+3
Zn?
+2
What is a Ligand?
a small molecule with a lone pair that can form a bond to a transition metal
H2O
NH3
Cl
What are 2 forms of transition metals?
Octahedral + Tetrahedral
what colour is
(Fe(H2O)6)2+
Pale green complex
what colour is
(Fe(H2O)6)3+
Yellow complex
What colour is (Cu(H2O)6)3+
Blue complex
What colour is
(Cr(H2O)6)3+?
dark green complex
What colour is (Co(H2O)6)2+?
Pink complwx
What does adding Ammonia solution to (Cu(H20)62+ cause?
4 ammonium molecules to replace the water molecules which form (Cu(NH3)4(H20)2+ which is a royal blue complex
What is cobalt chloride used for?
Test for H20
colour change is blue to pink
formula for it?
(CoCl4)2- —– (Co(H2o)6)2+
How is the complex formed?
when Cu2+ or Co2+ reacts with concentrated HCL which displaces the water molecules
this causes a colour change which is due to the absorption of light
Cu2+ goes from blue to yellow to green and cobalt goes from pink to blue
What is a ligand exchange?
when a transition metal ion is exposed to a mixture of ligands such as an aqeous solution of Chloride, ligands can be exchanged to form new complexes
This is Le chatelier’s principle
What is the equation for this?
(Cu(H20)6)2+ + 4NH3——(Cu(NH3)4(H2O)6)2+ + 4H2O
According to Le Chatelier’s principle what does adding ammonia do?
fores the equilibrium to the right, which produces more of (Cu(NH3)4(H2O2)2+
Adding water forces the equilibrIum to the left which produces more of Cu(H2O)2+
What is the equation?
(CoCH20)6)2+ + 4Cl- ——- (CoCl4)2- + 6H20
What is the colour of transition metal complexes?
always coloured but in the absence of ligands around the metal ion, the compound would be colourless
What effect does the ligands have when introduced to the metal ion?
a significant effect as without ligands, the transition metals have 5 degenerate orbitals where all the orbitals have the same energy
In an octahedral complex what happens?
6 negatively charged ligands approach the transition metals along the 3 axis DX, DY DZ
the negative charges repel the electrons in the orbitals which make the orbitals unstable and now no longer degenerate as each have a different energy
causing the 5 degenerate orbitals to split into 2 higher energy levels and 3 lower energy levels
What must an electron in the D Orbital now move from the lower to the higher?
gain energy through the absorption of light
When is only 1 frequency of light absorbed?
corresponds to the energy gap between the orbitals
energy is found from E=Hf
what does the D-D transition metals depend on?
the splitting and the D- orbitals and this varies between ions of different transition metals
What happens if the splitting varies?
the frequency of the colour of light absorbed also varies
Cu(H2O)6) 2+ is typically blue so absorbs all colours apart from blue
What does Cu+ complexes have?
a full D orbital so there are no empty orbitals to allow the electrons to move so Copper (I) does not absorb light in the visible range so appears colourless
What is Iron used in?
Haber Process to produce Ammonia from Nitrogen to Hydrogen
What is the formula?
N2(g) + 3H2(g)—-2NH3(g)
When is Nickel used?
Hydrogenation of vegetable oil to form margerine
When is Vanadium Oxide used?
in the contact process fot the production of H2SO4
MnO2?
used in the catalytic decomposition of H202
Why are Catalysts needed?
to save money, energy + time
What is a catalyst?
a substance which increases the rate of a chemical reaction by providing an alternate pathway with a lower activation energy
What is a homogenous catalyst?
A catalyst that is in the same physical phase as tHe reactants e.g V2O5
Heterogenous Catalyst?
a catalyst that is in a different state as the reactants
Why do transition meals act as Catalysts?
1) have empty orbitals
2) have variable oxidation states
What increases the reactivity of the bonded species?
when molecules with lone pairs can form coordinate bonds with the metal atom
or brings the 2 reactive molecules closer together
( heterogenous provide a solid surface where molecules = adsorbed)
Def of adsorbed?
attatched to the surface
What does having variable oxidation states do?
allow a metal ion to act as a catalyst in a redox reaction
(the metal is either the oxidising or reducing agent)
What do homogenous catalysts form?
coordinate bonds with the reactants and use their variable oxidation states to oxidise or reduce
Reaction of Cr3+ with NaOH?
ion = Cr3+
Colour of solution = pale green
Green/grey ppt is formed when NaOH is formed
when excess NaOH is added, ppt redissolves to form green solution
Reaction of Fe2+ with NaOH
Pale green solution
Dark green ppt is formed when NaOH is added
nvc in excess NaOH
Reaction of Cu2+ with NaOH?
colour of solution is blue
Pale blue PPT is formed when NaOH is added
NVC when IN excess NaOH
Equation for Cr3+?
Cr3+(aq) + 3OH-(aqO —— Cr(OHo3
GREEN GREY PPT
Cr(OH)3 + 3OH-)(aqO —– Cr(OH)6)3-
GREEN SOLUTION
Equation for Fe2+?
Fe2+(aq)+ 2OH-(aq) —–Fe(OH)2)S
DARK GREEN
Equation for Fe3+?
Fe3+(aq)+3OH-(aq)—- Fe(OH)3(s)
Rust brown
Equation for Cu2+?
Cu2+(aq) + 2OH-(aq) ——- Cu(OH)2(s)
pale blue
