Transition Metals Flashcards
Define a transition metal
d-block elements that form one or more stable ions with incompletely filled d-orbitals
What does it mean to show variable oxidation numbers
- transition metals forming multiple stable ions
- each ion the transition metal has a different oxidation number (e.g. vanadium has four stable oxidation numbers)
name 4 properties of transition metals
- variable oxidation numbers
- form complex ions
- ions are often coloured in solution
- act as good catalysts
why do transition metals show variable oxidation numbers
- transition metals form ions by removing electrons from both their 3d and 4s subshells
- these subshells are of similar energy levels
- so similar successive ionisation energies
what is a complex ion
central metal ion surrounded by dative covalently bonded ligands
what is a ligand
an atom, ion or molecule that donates a pair of electrons to a central metal atom or ion (forms a dative covalent bond)
name and define the three types of ligands
- monodentate –> ligands with one lone pair of e-
- bidentate –> ligands with two lone pairs of e- and can form two dative covalent bonds with the metal ion
- multidentate –> ligands with 2 or more lone pairs of e-
given an example of a bidentate ligand
1,2-diaminoethane
NH2CH2CH2NH2
Give an example of a multidentate ligand
EDTA4-
(hexadentate ligand)
give an example of a multidentate ligand in the body
- Haemoglobin an iron II complex containing multidentate ligand called a Haem group
- Haem group made up of a ring containing 4 N atoms ( can form 4 dative covalent bonds with Iron II )
define coordination number
number of dative covalent bonds formed with the central metal ion
what shape do six-fold coordination complexes have
octahedral
why do complexes with different coordination numbers have distinct shapes
- bonding electrons of the dative covalent bonds repel each other
- so ligands positioned as far away from each other as possible
what shape do four-fold coordination complexes have
tetrahedral
what ligand generally forms four-fold complexes
Cl- (large ligand)
most common shapes of coordination complexes
- octahedral
- tetrahedral
- square planar
what type of complex ions display what type of isomerism
- tetrahedral + square planar
- Cis/trans
what is used as a drug for cancer and what do you need to look out for with this drug
- cis-platin (a complex of platinum II)
- trans-platin is toxic, so must ensure only cis-platin is given to patients
What happens when ligands bond to transition ions
3d orbitals are split Into 2 different energy levels
What does the size of the energy gap between split 3d orbitals indicate
The frequency of light absorbed
What factors influence the amount of energy needed to make electrons jump up to the higher 3d energy levels
Of the central metal ion:
- oxidation number
- ligands
- coordination number