Transition Metals Flashcards
What is a complex
A species in which a number of molecules or anions are bonded to a central metal ion by dative covalent bond
Has no overall charge
What is a complex ion
Ion in which a number of molecules or anions are bound to a central metal atom by dative covalent bonds
Has an overall charge
What is a ligand
Molecule or anion that donates a lone pair of electrons to form a dative covalent bond with a central metal cation
What is Co- ordination number
The number of dative covalent bonds formed in a complex
What shape and bond angle is formed with a 6 co-ordination number
Octahedral
90degrees
What shape and bond angle is formed with a 4 co-ordination number
Tetrahedral
109.5 degrees
OR
Square planar
90 degrees
Which 4 co-ordinate number shape is most common and when is the other formed
Tetrahedral is more common
Square planar formed with two seperate monomers
What shape and bond angle is formed with a 2 co-ordination number
Linear
180 degrees
What is a monodenate ligand
Form one co-ordinate bond per ligand
What is a bidenate ligand
Forms two co-ordinate bonds per ligand
What is a multidenate ligand
Forms more than two co-ordinate bonds per ligand
When is E/Z isomerism used
When there are more than two different groups attached around a C=C double bond
What is cis/trans isomerism
When there are only two different groups around a C=C double bond
Formula shape and bond angle of cis-platin
[Pt(Cl)2(NH3)]
Square planar
90 degrees
Use of cis-platin
Can be used to stop replication of cancerous cells by binding to them
Why is trans platin not used
Toxic and ineffective drug
Why does the d-orbital split in transition metal complexes
When ligand approach the metal ion, electrons in the ligand repel the electrons in the d-orbital of the metal ion
Causes d sub-shell to split
Why is there colour in transition metal complexes
The electrons absorb UV and are excited into space in orbitals above
The change in energy due to this corresponds to UV/ visible light
Colour we see is a mixture of what is not absorbed
How is colour seen predicted
Using the colour wheel
Colour seen is opposite to colour absorbed
Why is no colour seen in Sc and why is it not a transition metal
No electrons to be promoted
Therefore no colour seen
Thus not a transition metal
Why is no colour seen in Zn and why is it not a transition metal
No space in d-orbitals for electron promotion
Therefore no colour
Thus not transition metal
Which subshell loses electrons first transition metal
4s electrons lost before 3d electrons
Definition of a transition metal
A transition metal is an element that has one or more stable ions with partially filled d orbitals
Colour of Cr 3+ ion
Violet
Colour of Fe 2+ ion
Green
Colour of Fe 3+ ion
Yellow
Colour of Cu2+ ion
Blue
Colour of Co2+ ion
Pink
Colour of Cr3+ and drops of NaOH/HCl
Green
Colour of Fe2+ and drops of NaOH/HCl
Green precipitate
Oxidises to brown in air
Colour of Fe3+ and drops of NaOH/HCl
Brown precipitate
Colour of Cu2+ and drops of NaOH/HCl
Blue precipitate
Colour of CO2+ and drops of NaOH/HCl
Blue precipitate
Colour of Cr3+ and excess NaOH
Green solution
Colour of Cr3+ and excess NH3
Purple solution
Colour of Cu2+ and excess NH3
Deep blue solution
Colour of Co2+ and excess NH3
Brown solution
Oxidises in air to form yellow solution
Colour of Cu2+ and conc HCl
Yellow
Colour of Co2+ and conc HCl
Blue solution
What factors affect the colour in a complex ion
The identity of the metal
Oxidation state of the metal
Identity of the ligands
Co- ordination number
What is Ligand exchange
When one or more ligands are replaced by other ligands
What can ligand exchange cause
A change in co-ordination number
A change in colour
When is ligand exchange actually acid base
When adding a few drops of OH- or NH3, the OH- or NH3 removes H+ ions from some of the water molecules
Reaction of hexaaquacopper and a few drops of dilute ammonia
[Cu(H2O)6]2+ + 2NH3 becomes [Cu(H2O)4(OH)2] + 2NH4+
Reaction of tetraaquabihydroxycopper and excess ammonia
[Cu(H2O)4(OH)2] +4NH3 becomes [Cu(NH3)4(H2O)2]2+ + 2H2O + 2OH-
Reaction of hexaaquacopper (II) and concentrated HCl
[Co(H2O)6]2+ + 4HCl becomes [Co(Cl)4] + 6H2O + 4H2
Why does hexaaquacopper (II) change into tetrachlorocuprate (II)
Because of the size of the Cl- ion, only four can fit around a central metal ion
