5.3 transition metals Flashcards
Define a transition metal
A d-block element that forms one or more stable ions with an incomplete d-subshell
What are the two d-block elements that aren’t transition metals?
Scandium and zinc.
Sc doesn’t form 2+ where only 4s electrons removed so no d-subshells filled when it forms 3+
Zn2+ only removes 4s electrons so d-block is filled completely.
Describe the physical properties of transition metals
-lustrous (shiny)
-high density
-high m.p & b.p
-conductive when in a giant metallic lattice
Describe the chemical properties of transition metals
-form coloured solutions when dissolved in water
-catalyse reactions
-variable oxidation states
What are the two ways transition metals can act as a catalyst?
Adsorption:
(where they provide a surface for the reaction to happen)
-reactants are adsorbed onto the surface of the transition metal and held there until the reaction finishes
-the reactants are then desorbed and metal remains unchanged
Variable oxidation states:
ability to change oxidation state by gaining or losing electrons means that they can bind to reactants, forming intermediates, providing an alternative reaction pathway with a lower activation energy.
examples of transition metals as catalysts?
-Haber process:
N2 + 3H2 -> 2NH3
Fe catalyst
-Contact process:
2SO2 + O2 -> 2SO3
Vanadium (V) Oxide catalyst
-Hydrogenation of alkenes:
Ni catalyst
-Decomposition of hydrogen peroxide:
Manganese (IV) oxide catalyst
Define a complex ion
A transition metal bonded to one or more ligands by coordinate bonds
Define a ligand
A molecule or ion that can donate one or more pairs of electrons to a transition metal ion to form coordinate bonds
Define a coordination number
The number of coordinate bonds between a central metal ion and its ligands
Define a coordinate bond
A bond in which one atom provides both the electrons in a covalent bond.
Give an example of a bidentate ligand
‘en’ NH2CH2CH2NH2
Name an example of a square planar complex ion
Pt(NH3)2Cl2
(I think anything involving Pt)
Describe the role of cis-platin
Binds to DNA of cancer cells to stop them dividing, the cells will then undergo apoptosis.
Define a ligand substitution reaction
A reaction in which one ligand in a complex ion is replaced by another
Reaction of Cu2+ with NH3
(excess and dropwise)
colours?
Dropwise…
[Cu(H2O)6]2+ + 2NH3 -> Cu(H2O)4(OH-)2 + 2NH4+
Cu(H2O)4(OH-)2 + 4NH3 -> [Cu(H20)2(NH3)4]2+ + 2H2O + 2OH-
Excess…
[Cu(H2O)6]2+ + 4NH3 -> [Cu(H2O)2(NH3)4]2+ + 2H2O
[Cu(H2O)6]2+ = blue solution
[Cu(H20)2(NH3)4]2+ = deep blue solution
Cu(H2O)4(OH-)2= blue ppt.
Cu2+ + HCl
colours?
[Cu(H2O)6]2+ + 4Cl- -> [CuCl4]2- + 6H2O
[Cu(H2O)6]2+ = blue solution
[CuCl4]2- yellow solution
Cu2+ + NaOH
colours?
[Cu(H2O)6]2+ 2OH- -> Cu(H2O)4(OH-) +2H2O
[Cu(H2O)6]2+ = blue solution
Cu(H2O)4(OH-) = blue ppt.
Fe2+ + NaOH
colours?
[Fe(H2O)6]2+ + 2OH- -> Fe(H2O)4(OH-)2 + 2H2O
[Fe(H2O)6]2+ = green solution
Fe(H2O)4(OH-)2 = green ppt
Fe2+ + NH3
colours?
[Fe(H2O)6]2+ + 2NH3 -> Fe(H2O)4(OH-)2 +2NH4+
[Fe(H2O)6]2+ = green solution
Fe(H2O)4(OH-)2 = green ppt
Fe3+ + NH3
colours?
[Fe(H2O)6]3+ + 3NH3 -> Fe(H2O)3(OH)3 + NH4+
brown solution -> brown ppt
Fe3+ + NaOH
colours?
[Fe(H2O)6]3+ + 3OH- -> Fe(H2O)3(OH)3 + 3H2O
Mn2+ + NH3
colours?
[Mn(H2O)6]2+ + 2NH3 -> Mn(H2O)4(OH)2 + 2NH4+
pale pink solution -> pale brown ppt.
Cr3+ + NaOH
colours?
[Cr(H2O)6]3+ + 3OH- -> Cr(H2O)3(OH)3 + 3H2O
green solution -> green ppt.
Cr(H2O)3(OH)3 + 3OH- -> [Cr(OH)6]3- + 3H2O
green ppt. -> dark green solution
Mn2+ + NaOH
colours?
[Mn(H2O)6]2+ + 2OH- -> Mn(H2O)4(OH)2 + 2H2O
pale pink solution -> pale brown ppt.
