23. Transition metals Flashcards
Define a transition metal
An element that forms at least one stable ion with a part full d-shell of electrons
Why is Scandium (21) not a transition metal
Only forms Sc3+ (3d0) which does not have a partially filled d orbital so is not a transition metal
Why is Zinc (30) not a transition metal
Only forms Zn2+ (3d10) which does not have a partially filled d orbital so is not a transition metal
Name the 4 main features which are common to transition metals
- variable oxidation states
- coloured
- catalysts
- complex formation
What does complex formation mean
Transition elements form complex ions
What is a complex ion
A complex ion is formed when a transition metal ion is surrounded by other ions or molecules (ligands) which are bonded by coordinate bonds
What is a ligand
An ion or molecule with a lone pair of electrons that forms a co-ordinate bond with a transition metal
What is the co-ordination number
The number of co-ordination bonds to ligands that surround the transition metal ion
Ions with co-ordination number six are usually…
Octahedral
Ions with co-ordination number four are usually…
Tetrahedral
Some ions with co-ordination number four are usually…
Square planar
What happens when you dissolve the salt of a transition metal ion water
The positively charged ion becomes surrounded by water molecules that act as ligands. These are called aqua ions.
What is an aqua ion
- when you dissolve the salt of a transition metal ion water
- the positively charged ion becomes surrounded by water molecules that act as ligands
What is a multidentate ligand
A molecule or ion that have more than one atom with a lone pair of electrons which can bond to a transition metal ion
Give 3 examples of bidentate ligands
- ethane- 1,2-diamine
- ethanedioate ion
- benzene- 1,2-diol
Name an important multidentate ligand that can act as a hexadentate ligand
EDTA 4-
What are chelates
Complex ions with polydentate ligands
What can chelates be used for
Remove d-block metal ions from solution
What will happen when you add a hexadentate ligand into a solution of transition metal salt
It will replace all six water ligands
Why is chelate complexes with polydentate ligands favoured over complexes with monodentate ligands
When polydentate ligands replace the monodentate ligands there is an increase in the number of particles and therefore entropy so it is the favourable reaction
What is the chelate effect
When chelate complexes with polydentate ligands favoured over complexes with monodentate ligands due to entropy
What shape is [Co(NH3)6]3+
Octahedral as it has 6 ligands
What shape is [CoCl4]2-
Tetrahedral as it has 4 ligands
What type of isomerism occurs in octahedral and square planar complexes
E-Z (geometrical)