5.3.1 Transition metals Flashcards
(43 cards)
What are d block elements?
- between Grp 2 and 13, with highest energy electrons in 3d orbitals
- metallic: high mp and bp, shiny, and conduct electricity and heat
Write out the electronic configurations for copper and chromium?
Cr: 1s2 2s2 2p6 3s2 3p6 3d5 4s1
Cu: 1s2 2s2 2p6 3s3 3p6 3d10 4s1
for stability
Whats special about ions forming with d block elements? E.g. give electronic configuration of Fe2+
- they lose 4s e- first before losing 3d
1s2 2s2 2p6 3s2 3d6
Define transition elements
- d block elements that form at least one ion with partially filled d-orbital (scandium and zinc are NOT transition metals)
State and describe the 3 properties of transition metals
- variable oxidation numbers -> all form +2 in compounds, manganese up to +7
- coloured compounds -> colour linked to partially filled d-orbitals of transition metal ion + can vary with diff oxidation states
- catalysts
heterogenous
- haber: iron
- hydrogenation: nickel
- hydrogen peroxide decomposition: MnO2
- contact process: V2O5
homogenous
- Fe2+ ions in reaction of iodide ions and S2O8 2-.
Define ligand
molecule/ion that donates a pair of electrons to a central metal ion to form a coordinate/ dative covalent bond to form a complex
Define coordination number
indicates the no. of bonds attached to the central metal ion
What is monodentate vs bidentate? What are the key examples?
mono: donate ONE pair of electrons to central metal ion (water, ammonia, OH-, Cl-)
bi: donate TWO pairs of electrons to central metal ion (C2O4 2-, NH2CH2CH2NH2)
How do you represent complex ions?
[Cr(H2O)6] 3+
ion inside square brackets
ligand inside round brackets
What is the shape for coordination numbers:
a) 6
b) 4
c) 2
a) octahedral (90 degrees)
b) tetrahedral (109.5 degrees) or square planar (90 degrees) when there are 8 d electrons in the highest energy d sub shell
c) linear (180 degrees)
Which shape complex ions show cis-trans isomerism?
Some four (square planar) and six coordinate (octahedral) complex ions with 2 diff monodentate ligands
Which shape complex ions show cis-trans AND optical isomerism?
Some six-coordinate complex ions containing monodentate and bidentate ligands
Optical isomerism only in octahedral complexes containing 2 or more bidentate ligands e.g. 3
What is cis platin used for?
Used as an anti cancer drug since it forms a complex in a cell which binds to DNA and prevents it from replicating
Describe the cis vs trans isomer for octahedral monodentate and bidentate e.g. using angles
Cis: 90 degrees between the same type of ligand (they’re next to each other)
Trans: 180 between the same type of ligand (opposite each other)
Bidentate is the same thing
What is ligand substitution?
One ligand in a complex ion is replaced by another ligand
Copper (II) sulfate in water forms which ion?
[Cu(H2O)6] 2+
[Cu(H2O)6]2+ colour
Pale blue
Write equations for ligand substitutions of [Cu(H2O)6]2+ (e.g with ammonia and with HCl)
What happens when dropwise ammonia is added compared to excess?
EXCESS AMMONIA:
[Cu(H2O)6]2+ +4NH3 -> [Cu(NH3)4(H2O)2]2+ + 4H2O
With dropwise ammonia added, Cu(OH2) precipitate forms then dissolves in excess ammonia to form the complex ion
EXCESS CONC HCL:
[Cu(H2O)6]2+ +4CL- <-> [CuCl4]2- + 6H2O (green intermediate due to mixture of solutions)
[Cu(NH3)4(H2O)2]2+ colour
Dark blue
Cu(OH)2 Colour
Pale blue
[CuCl4]2- colour
Yellow
Water + [CuCl4]2- forms what?
Goes back to blue Colour but more dilute/paler
Why does coordination number change when HCl is added?
Since chloride ligands are larger so fewer can fit around central ion compared to water molecules in copper(II) sulfate complex ion
KCr(SO4)2 . 12H2O in water = [Cr(H2O)6]3+ and which Colour?
Violet
