Topic 17: Transition Metals & their Chemistry

Transition Metals:

d-block elements that form one or more stable ions with incompletely-filled d-orbitals

explain why transition metals have Variable Oxidation States

4s electrons have lower energy than 3d electrons, so they fill before the 3d orbitals. However, once the 3d orbitals start filling, the 4s orbital becomes higher in energy, so its electrons are removed first.

explain why transition metals produce colors

color is due to splitting of 3d orbital; by ligands so different energy difference between d-orbitals lead to different frequencies of light being absorbed and reflected

Ligand

molecule that forms coordinate bond with a central transition metal ion

Complex ion

central metal ion surrounded by ligands

Describe Octahedral Shape

6 ligands, and 6 donated electron pairs

90º bond angle

ex. [Mn(H2O)6]2+ , [Fe(H2O)4(OH)2] , [Cr(OH)6]3-

Describe Tetrahedral Shape

ex. only [Cu(Cl)4]2-

Describe Linear Shape

ex. only tollen’s reagent [H3N → Ag ← NH3]+

Square Planar Shape

ex. cis-platin used in cancer treatment

[2NH3 → Pt ← 2Cl]

Colors of Vanadium Oxidation States

VO2 + / VO3 - (5+) yellow

VO2+ (4+) blue

V3+ green

V2+ purple

Colors of Chromium Oxidation States

Cr2O7 2- (6+) orange

Cr3+ green

Cr2+ blue

hexaaquachromium + NaOH

intermediate: [Cr(H2O)3(OH)3]

end product: [Cr(OH)6]3-

hexaaquachromium + NH3

intermediate: [Cr(H2O)3(OH)3]

end product: [Cr(NH3)6]3+

hexaaquachromium + H2O2/OH-

intermediate CrO4 2-

end product: Cr2O7 2-

Reactions of Transition Metals