Chapter 24 Transition Elements

Elements found between group 2 and group (1)3 Highest energy electron found in a d orbital

Cr= …3d5 4s1 Cu= 3d10 4s1 Half or full d sub shell more stable than not, and so electron excites from the 4s orbtial

4s It’s why a lot of d block elements have 2+ ions Filling 4s first, also empties first as the energy of the 3d falls below that of the 4s when both are filled

D block elements that form at least 1 ion with a partially full d-orbital Zinc - only Zn2+ so a full d sub shell Sc- not Sc3+, so an empty d sub shell

Cr2+ = light blue Cr3+ = dark Green Cr4+ and Cr5+ = colourless Cr6+ = orange or yellow

Transition metals in high oxidation states are good oxidising agents as the metal complex wants to be reduced E.g MnO4- +7 wants to be Mn2+

Haber Process- N2 + 3H2 —/2NH3. Catalysed by Fe Contact Process- 2SO2 + O2 —/2SO3 Catalysed by V2O5 Iodide-peroxydisulphate- catalyses by Fe2+

Central metal ion with one or more ligands bound to it by dative covalent bonds

A molecule or ion that donates a one pair of electrons to a central metal ion via dative covalent bonding

Square brackets around the whole complex Round brackets for the ligands Charge on the outside E.g [Cr(NH3)6] 3+

The number of dative covalent bonds made to a central metal ion in a complex ion

6-Octahedral 4- usually tetrahedral But if 8 d electron in the ion, becomes square planar Usually Pt, Au(III) Pd

A ligand which is able to donate 1 lone pair of electrons to a central metal ion, forming 1 coordinate bond e.g ammonia A ligand which is able to donate 2 lone pairs of electrons to a central metal ion via dative covalent bonding e.g ethanedioate

When there no more than 2 identical ligands Cis/Trans Same side= Cis, 90 degrees Opposite side= trans, 180 degrees

When two identical ligands and 2 bidentate ligands Or 4 identical and 2 different Same monodentate = 90 degrees, Cis Opposite monodentate= 180 degrees, Trans

Mirror images are not superimposable In Cis 2 bidentate and 2 monodentate And 3 bidentate Draw the mirror image

[Pt(NH3)2Cl2] Anti-cancer drug which inhibits cell division, shrink tumour sizes but lots of side effects Forms a complex with guanine where the Cls are substituted by the nitrogen’s in the base, prevents DNA replication and triggers apoptosis

When one ligand is swapped for another

Originally Cr3+ Violet Dropwise- base, hydroxide Cr3+ + 3OH- —/ Cr(OH)3 (s). Grey green Excess, full substitution Cr(OH)3 + 6NH3 —/ [Cr(NH3)6]3+ + 3 OH- Purple

Grey-Green to Dark Green Cr(OH)3 + 3OH- —/ [Cr(OH)6]3-

[Cu(H2O)6]2+ pale blue Dropwise Cu(H2O)6 + 2OH- —/ Cu(OH)2(H2O)4 + 2H2O Blue precipitate Excess Cu(OH)2(H2O)4 + 4 NH3 —/ [Cu(H2O)2(NH3)4]2+ + 2OH- + 2H2O. Dark Blue solution Pale blue solution, then blue precipitate, then dark blue solution, partial substitution

[Cu(H2O)6]2+ + 4Cl- —/ [CuCl4]2- + 6H2O Pale blue to Yellow Change in coordination number as the chloride ligands are larger than water, physically not enough space for 6 of them

Fe2+ + 2OH- /=/ Fe(OH)2 Reversible reaction, adding acid decreases the concentration of hydroxide Pushes the position of equilibrium to the left, so more ions less precipitate

Pale Green solution Green precipitate Insoluble