Topic 23: The Transition Metals Flashcards
(21 cards)
Transition Element Definition
An element that forms at least one stable ion with a part full d-shell of electrons.
4 Main properties of transition metals
-Variable oxidation states - many redox reactions
- Colourful
- Catalysts
- Form complexes
Transition metal complex
A transition metal atom or ion surrounded by molecules or ions called ligands which form coordinate bonds
Ligand
An atom or atom group that can donate a lone pair of electrons to a transition metal ion to form a complex through the formation of co-ordinate bonds
Coordination number
The number of bonds to the central metal atom by ligands
Shapes of complexes
Octahedral
Tetrahedral
Square planar
Linear
Aqua ions
Salt of a transition metal ion dissolved in water it will form a aqua complex with (usually) 6 water ligands surrounding it. (Hexaaqua complex)
[Cu(H2O)6]^2+
Multidentate ligands
More than one atom with lone pair which can bond to a transition metal ion
En
Ethylene diamine
Bidentate ligand (2 lone pairs)
Neutral
Ethane-1,2-diamine
Ethanedioate ion
(Oxalate ion) C2O4^2-
Bidentate ligand
Lone pairs on the singly bonded Os
Benzene-1,2-diol
Neural bidentate ligand
ETDA^4-
Hexadentate ligand
Lone pairs on 4 Os and 6 Ns
The chelate effect
The replacement of monodentate ligands with bidentate and multidentate ligands in complex ions.
It is favourable as there are more particles after than before as all of the (usually) water ligands have been replaced this increases the entropy of the reaction making it more favourable.
Chelates
Complex ions with polydentate ligands.
Effective at removing d block metal ions from solution.
Why chlorine forms tetrahedral structure
The chloro ligand is larger so fewer ligands can fit around the central metal ion
Isomerism in complexes
Geometric - ligands in different places on the complex - oppposite or next to each other
Optical - Non-superimposable mirror images of each other - two or more bidentate ligands in a complex.
How we see colour
Absorbs all the light that aren’t it’s colour and transmits the light that is its colour
Why transition metal complexes are coloured
- absorb wavelengths of visible light
-d orbital splits
-electrons move from grounded state to excited state - remaining wavelengths of visible light transmitted
MIGHT WANNA CHECK UP ON THIS
Working out frequency of light equation
ΔE = hv
ΔE - energy gap
h = Planck’s constant
v = frequency of light
Colorimetry
Dilution series and calibration curve
