Transition Metals Flashcards
A transition elements is a d block element that:
Forms at least one ion with a partly filled d sub shell.
Transition elements…
Cu, Ti, V, Cr, Mn, Fe, Co
D block elements that are not transition elements…
Sc and Zn
Why are Sc and Zn not transition elements even though they’re in the D block?
Sc3+ is an ion with no d electrons.
Zn2+ has a completely filled d orbital.
Why is 4s electron sub shell filled before 3d?
4s orbitals have a lower energy than the 3d, and so is filled first.
What is the electronic configuration of chromium (Z = 24)?
1s2 2s2 2p6 3s2 3p6 4s1 3d5
What is the electronic configuration of copper (Z = 29)?
1s2 2s2 2p6 3s2 3p6 4s2 3d10
What is the electronic configuration of Cu2+ ion (copper = 29)?
1s2 2s2 2p6 3s2 3p6 4s0 3d9
Give 4 properties of transition elements?
- They form coloured compounds.
- They form complex with ligands.
- They are good catalysts.
- They can show several different oxidation states in their compounds.
Why are transition elements effective catalysts?
They can change oxidation state easily.
What is the equation for the Haber process?
N2 (g) + 3H2 (g) -> 2NH3 (g)
What is the catalyst in the Haber process?
Fe
What is the process that manufactures H2SO4 called?
The contact process.
What is the equation for the contact process?
2SO2 (g) + O2 (g) -> 2SO3 (g)
What is the catalyst in the hydrogenation of alkenes?
Nickel
What is the equation for the decomposition of hydrogen peroxide?
2H2O2 (aq) -> 2H2O (l) + O2 (g)
What is the catalyst for the decomposition of hydrogen peroxide?
MnO2.
Definition of a ligand.
A molecule or ion that can donate a pair of electrons to a transition metal ion.
Definition of coordination number.
The total number of coordinate bonds formed between the central metal ion and any ligands.
What is a complex ion?
A transition metal ion bonded to one or more ligands by coordinate bonds.
Why does the platin complex ion not have an overall charge?
The 2+ charge on platin is cancelled out by the 2Cl-
What is a monodentate ligand?
Ligand donates one pair of electrons to central metal ion (forms one coordinate bond).
What is a bidentate ligand?
Ligand donates 2 pairs of electrons to central metal ion (forms two coordinate bonds).
What is the observation of Cu2+ with OH-?
Pale blue solution forms pale blue precipitate.
What is the observation of Co2+ with OH-?
Pink solution forms blue precipitate- turns beige in air.
What is the observation of Fe2+ with OH-?
Pale green solution forms dark green precipitate- turns brown in air.
What is the observation of Fe3+ with OH-?
Pale yellow solutions form red/brown precipitate.
What is the equation of Cu2+ with OH-?
Cu2+ (aq) + 2OH-(aq) -> Cu(OH)2(s)
What is the equation of Co2+ with OH-?
Co2+ (aq) + 2OH-(aq) -> Co(OH)2(s)
What is the equation of Fe2+ with OH-?
Fe2+ (aq) + 2OH-(aq) -> Fe(OH)2(s)
What is the equation of Fe3+ with OH-?
Fe3+ (aq) + 3OH-(aq) -> Fe(OH)3(s)
Define ligand substitution.
A reaction in which one ligand in a complex ion is replaced by another ligand.
What is the observation of Cu2+ with ammonia?
Pale blue solution forms light blue precipitate which redissolves to form dark blue solution.
What is the equation of Cu2+ with ammonia?
[Cu(H2O)6]2+ + 4NH3 -> [Cu(NH3)4(H2O)2]2+ + 4H2O
What is the observation of Cu2+ with conc HCl?
Pale blue solution changes to a yellow solution and finally a green solution.
What is the equation of Cu2+ with conc HCl?
[Cu(H2O)6]2+ + 4Cl- -> [Cu(Cl)4]2- + 6H2O
What is the observation of Co2+ with conc HCl?
Pale pink solution changes to a blue solution.
What is the equation of Co2+ with conc HCl?
[Co(H2O)6]2+ + 4Cl- -> [CoCl4]2- + 6H2O
Define stability constant.
The equilibrium constant for the formation of the complex ion from its constituent ions in solution.
With reference to oxidation states and colours of compounds, explain why iron is a typical transition metal and aluminium is not.
Iron can exist in two different oxidation states- aluminium only one.
Iron can form coloured compounds/solutions- aluminium forms only colourless.
What is a coordinate bond?
A covalent bond in which both electrons in the shared pair come from the same atom.
What shape are 6 coordinate bonds?
Octahedral
What shape are 4 coordinate bonds?
Tetrahedral (sometimes square planar)
What is optical isomerism?
A type of stereoisomerism- it happens when an ion can exist in two non superimposable mirror images.
Why is cis platin so important?
It can prevent DNA of cancerous cells reproducing by division.
Give an example of 6 coordinate bonds (octahedral shape)
[Cu(H2O)6]2+
[Co(NH3)6]2+
Give an example of 4 coordinate bonds (tetrahedral shape)
[CuCl4]2-
Give an example of 4 coordinate bonds (square planar shape)
[NiCl2(NH3)2]
Cu2+ Reactions…
- With NaOH
- With HCl
- With NH3
NaOH
Precipitaiton reaction
Blue to Blue ppt
Cu2+(aq) + 2OH- (aq) -> Cu(OH)2 (s)
HCl
Blue to Green
[Cu(H2O)6]2+ + 4Cl- -> [Cu(Cl)4]2- + 6H2O
NH3 (conc/ excess dilute)
Blue to dark blue
[Cu(H2O)6]2+ + 4NH3 -> [Cu(H2O)2(NH3)4]2+
What is cis-platin?
A complex of platinum (II) with two chloride ions and two ammonia molecules in a square planar shape.
How does cis platin work?
The two Cl ligands are easily displaced, so cis platin loses them.
It then bonds to two N atoms on the DNA molecule of the cancerous cell instead.
This block will prevent cancerous reproduction.
Give two examples of oxidising agents.
KMnO4
K2Cr2O7
How do you carry out a redox titration with manganate (VIII) ions as the oxidising agent?
Measure out a quantity of reducing agent, eg Fe2+ ions.
Add dilute H2SO4 and
Using a burette, add MnO4- (aq), swirling
Stop when end point is reached
Repeat
Write a half equation to show manganate (VII) ions acting as an oxidising agent.
MnO4- + 8H+ + 5e- -> Mn2+ + 4H2O
5Fe2+ -> 5Fe3+ + 5e-
MnO4- + 8H+ + 5Fe2+ -> Mn2+ + 4H2O + 5Fe3+
