Topic 15- Transitition Metals Flashcards
Where can Transition Metals be found?
d-block
Describe the electron configuration of Chromium
one electron in each orbital of 3d sub shell (3d5) and ONE in the 4s. This is due to greater stability having an electron in each orbital of the 3d sub shell.
When transition metals form positive ions which electrons from which shells are removed first?
outer ‘s’ electrons are removed first. Then the d electrons.
Which metals aren’t transition metals and WHY?
Scandium and Zinc. Sc only forms a positive ion (Sc 3+) which has an empty d subshell. Zn only forms Zn 2+ which results in a full d subshell
Define a Transition metal
d-block elements that can form one or more STABLE ions with incompletely filled d-orbitals.
What is a complex ion?
A metal ion surrounded by dative covalently bonded ligands.
What is a ligand?
An atom, ion or molecule that donates a lone pair of electrons to a central metal atom/ion.
Name the 3 types of ligand
Monodentate (1 lone pair)
Bidentate (2 lone pairs)
Multidentate (more than two lone pairs)
How can you calculate the overall charge on a complex ion?
work out oxidation number which is
total oxidation number - sum of charges of ligands
What is the coordination number?
The number of dative covalent bonds formed with central metal ion.
What 3 shapes can complexes form?
Square planar-90
Tetrahedral-109.5
Octahedral-90
What happens to the 3d sub shell as ligands come and bond to the ions?
the 3d sub shell split into two different energy levels?
Why is Zn not a transition metal?
Zn can only form a +2 ion where the Zn2+ ion has a complete d orbital.
Why is Sc not a transition metal?
Sc can only form a +3 ion. In this ion Sc3+ has an empty d orbital so isn’t a transition metal.
Describe the successive ionization energies for the elements Sc to Zn.
They show a gradual increase in ionisation energy until all the 4s and 3d electrons have been removed.
Then a big jump as e-‘s removed from inner core electrons.
Colour changes arise from changes in…
Oxidation state, coordination number, ligand.
What is cisplatin?
An anti-cancer drug
Name properties of Transition Metals
Hard, Shiny, Good thermal & electrical conductors.
Multiple oxidation states, form coloured ions in solution, good catalysts, form complexes with ligands.
What is a heterogeneous catalyst?
A catalyst which is in a different phase to the reactants (e.g. solid and liquid)
If we increase the surface area, the rate of reaction increases. Why is this?
More reagents can adsorb
The contact process converts …. into ….. which is then converted to …… ….. using water. The catalyst is…
The contact process converts Sulfur dioxide into sulfur trioxide and then into sulfuric acid. The catalyst is V2O5
The contact process is an example of a reaction that uses a ……… ……
Heterogeneous catalyst
Catalyst poisoning can happen when …
Another molecule irreversibly adsorbs onto the surface of the catalyst as it stops reactants from adsorbing.
What is a homogeneous catalyst?
A catalyst which is in the same phase as the reactant e.g. two aqueous solutions
How do catalysts work?
By changing oxidation state. as they donate or accept electrons to oxidise or reduce a species.
What colour is Vanadium (IV) (VO2+)
Blue
What colour is Vanadium (II)
Violet
What colour is Vanadium (III)
Green
What colour is Vanadium (V) (VO+)
Yellow
Transition metals can have multiple …. …. in a number of …… states
Transition metals can have multiple stable ions in a number of oxidation states.
How can you prepare different ions of vanadium?
By successive reduction with zinc in acid solution.
What do redox potentials show you?
How easily a metal can be reduced.
Name 3 common ligands
H2O, NH3, Cl- (biggest)
The coordination number doesn’t change when substituting water for ammonia. Why?
Because they are of a similar size (if Cl- was substituted then it would change)
A ligand that can form two bonds is called….
Bidentate
A ligand that can form one bond is called….
Monodentate
A ligand that can form multiple bonds is called….
Multidentate
What does denticity describe?
The number of dative bonds that can be formed with a transition metal by one ligand.
Name 2 factors that influence the shape of complex ions.
- Metal
2. Ligand
What type of ligand is H₂NCH₂CH₂NH₂
bidentate
What colour change would you observe in the following reaction? [Cu(H₂O)₆]²⁺ + 4Cl ⁻ ⇌ [CuCl₄]²⁻ + 6H₂O
pale blue solution to yellow/green solution
- In which order are the third and fourth level s, p and d electrons lost? (First:Last)
4s, 3d, 3p, 3s
In which order are the third and fourth level s, p and d electrons filled in? (First:Last)
3s, 3p, 4s, 3d
Describe what a catalyst in catalytic converters in motor cars does.
It converts nitrogen oxides and carbon monoxide to nitrogen and carbon dioxide by adsorbing the reactants on its surface so weakening their bonds
Describe Cis-platin
3 ) Pt(NH3 )2Cl2 with cis geometry. An anticancer compound that binds to the two strands of DNA during cell division process. This prevents them from separating and hence stops the cell division.
Ligand exchange?
A reaction in which a ligand is substituted by another ligand.
Adsorption
The process of forming weak bonds by reactants to a surface of a solid catalyst
Desorption
The reverse process to adsorption. Adsorbed molecules leave the surface
Autocatalysis
When a product of a reaction catalyses the reaction, e.g. Mn 2+ in oxidation of c2o4 (2-) with Mno4- under acidic conditions.
Colour of Cr3+?
Green
Colour of Fe3+
yellow
Colour of Fe2+
Pale green
Colour of Co2+
pink
Colour of Cu2+
pale blue
Colour of Cr2O7 ^2-
Orange
How does the fact that transition metals have partially filled d-orbitals help it act as a heterogenous catalyst?
The orbitals allow reactant molecules to make weak bonds to the catalyst
Explain how adsorption helps to catalyse the reaction.
The surface of the catalyst activates the molecules, weakening the bonds between the atoms in the reactants, making them easier to break and reform as products
What is a dative covalent bond?
A covalent bond in which both electrons in the shared pair come from the same atom
What shape molecule is cis-platin?
Square Planar
What colour is the ion of a CrO4-?
Yellow
What colour is the ion of a Cr3+?
Violet is surrounded by 6 water ligands
Green if substituted with impurities ie Cl-
What colour is the ion Cr2+
Blue
Chromium Hydroxide is Amphoteric. What does this mean?
Reacts with both acids and bases
If you add excess ammonia to chromium hydroxide precipitate a …… ….. …. occurs
If you add excess ammonia to chromium hydroxide precipitate a ligand exchange reaction(substitution) occurs
Transition metal ions form tetrahedral complexes with …….. ligands such as …
Transition metal ions form tetrahedral complexes with LARGE ligands such as Cl-
What type of ligand is NH2CH2CH2NH2 ?
Bidentate
What type of ligand is EDTA 4- ?
Multidentate
The catalysed reaction with a homogeneous catalyst proceeds via an ………. …….
Homogeneous catalysts proceed via an intermediate species
Why do transition metals show multiple oxidation numbers?
able to donate and receive electrons and are
able to oxidize and reduce because partially filled sub-shells of d electrons easily lose or gain electrons. Energy differences between the oxidation states are small
What is the reason behind a CHANGE in colour of an ion?
Changing a ligand or changing the coordination number as it alters energy split therefore the frequency of light absorbed
Which transition metal ion can form LINEAR complexes?
Ag+ , e.g. [Ag(NH3)2]+,[Ag(S2O3)2]3- and
[Ag(CN)2]- (all colourless)
Why does Cisplatin have to have cis geometry?
The cisplatin version only works as two chloride ions are displaced and the molecule joins on to the DNA.
Transplatin IS TOXIC
Is there an overall change in oxidation number during a catalysed heterogeneous reaction?
NO
Copper(II) Sulfate solution is blue. This is because…
electrons absorb light in the red region of the spectrum and the residual frequencies are observed.
What can result in the change in colour of transition metal ions?
Change in ligand
Change in oxidation state
Change in coordination number
How does Carbon monoxide poisoning occur?
CO replaces an oxygen/H2O molecule which forms a STRONGER bond with the iron so won’t readily exchange with oxygen so Haemoglobin can’t transport oxygen anymore.
………. ligands will almost always displace ……… ligands at a metal centre
multidentate ligands will almost always displace monodentate ligands at a metal centre
Which 3 metal ions form linear complexes?
Cu, Ag, Au
How do variable oxidation states arise?
Arises from the similar energies required for removal of 3d and 4s electrons.
What is the colour change of [CuCl4] 2- —-> [Cu(H2O)6] 2+
Yellow to blue
What is the colour change of [Cu(NH3)4(H2O)2) 2+ —-> [Cu(H2O)6] 2+
Deep blue to pale blue
What is the colour change of [CoCl4] 2- —–> [Co(H2O)6] 2+
Blue to Red
Which two metal hydroxides undergo a ligand exchange reaction in excess ammonia?
[Co(OH)2(H2O)4] + 6NH3 -> [Co(NH3)6] 2+
blue precipitate dissolves to form a yellow-brown sol
[Cu(OH)2(H2O)4] + 4NH3 -> [Cu(NH3)4(H2O)2] 2+
blue precipitate goes to deep blue solution
Colour change of
[Cu(H2O)6]2+ +2OH- –> [Cu(OH)2(H2O)4] +2H2O
Pale blue solution turns to blue precipitate.
Colour change of
[Fe(H2O)6]2+ +2OH- –> [Fe(OH)2(H2O)4] +2H2O
Pale green solution turns to green precipitate which darkens on standing
Colour change of
[Fe(H2O)6] 3+ + 3OH- –> [Fe(OH)3(H2O)3] +3H2O
Yellow solution to orange precipitate and darkens on standing
Colour change of
[Co(H2O)6]2+ +2OH- –> [Co(OH)2(H2O)4] +2H2O
Pale pink solution to a blue precipitate which turns brown on standing.
To form a compound or complex containing an ion the energy given out needs to…… than the energy taken to remove the outer electrons.
Energy given out should be greater than energy taken to remove outer electrons
