NOT DONE2.5 Transition Metals Flashcards
What are transition metals?
Elements in d block with a partially filled d-orbital
Lose electrons to form positive ions with s-orbital electrons being removed first
What is similar about all transition metals?
Atomic radius
High density
High melting/boiling point
Give four chemical properties of all transition metals.
Form complexes
Form coloured ions
Variable oxidation states
Good catalysts
What is a transition metal complex?
A central metal atom or ion surrounded by ligands
What is a ligand?
A molecule or ion with a lone pair of electrons
How do transition metal complexes form?
An electron pair is donated to the central metal ion from the each ligand to form a coordinate bond
What is a ligand substitution reaction?
Exchange of a ligands without a change in coordination number
What is a coordination number?
The number of coordinate bonds formed around a central metal ion
What is produced in an incomplete ligand substitution reaction?
A combination of ligands around the central ion
What is a bidentate ligand?
Ligand able to form two coordinate bonds to the central metal ion as they have two lone electron pairs
Describe how bidentate ligands change coordination number.
Can replace two unidentate ligands without changing coordination number as same number of bonds form
What is a multidentate ligand?
Ligands able to form up to six coordinate bonds to the central metal ion as they have multiple lone electron pairs
Name two common multidentate ligands.
EDTA
Haem
Why is haem a component of haemoglobin?
It consists of six coordinate bonds around a central Fe²⁺ ion
Its shape and structure allow it to transport oxygen around the body
Why is carbon monoxide toxic to humans?
Replaces the oxygen in the haem complex preventing it from being transported around the body
What is The Chelate Effect?
The replacement of monodentate ligands with bidentate and multidentate ligands in complex ions
What is the purpose of The Chelate Effect?
An energetically favourable reaction as ΔG is negative
A greater energy change means a more stable complex is formed and ΔG is more negative
What enthalpy change do ligand substitution reactions have?
Near zero as bonds formed are very similar to bonds broken
What shape do transition metal complexes commonly have?
Octahedral
Bond angle of 90°
What is cis-trans isomerism?
Isomerism shown by octahedral complexes with different types of unidentate ligands
What is a trans isomer?
Isomer has two of the same ligands opposite each other
What is a cis isomer?
Isomer has two of the same ligands next to each other
What is optical isomerism?
Isomerism shown by octahedral complexes with bidentate ligands
Two isomers are mirror images of each other
What shape do transition metal complexes with larger ligands have?
Tetrahedral
Bond angle 109.5°
