S Block Flashcards
What is a transition metal?
An element that possesses a partially filled d sub-shell in its atom or stable ions.
Which electrons are lost first when removing electrons from transition metals?
The 4s electrons are lost first.
What is the electronic configuration of Scandium (Sc)?
[Ar] 3d¹ 4s²
Why is Scandium considered a transition metal?
Because its atom has an incomplete d sub-shell.
What is the electronic configuration of Copper (Cu)?
[Ar] 3d¹⁰ 4s¹
Why is Copper considered a transition metal?
Because its 2+ ion has an incomplete d sub-shell.
What is the electronic configuration of Zinc (Zn)?
[Ar] 3d¹⁰ 4s²
Is Zinc a transition metal? Why or why not?
No, because neither its atom nor its ion has an incomplete d sub-shell.
What allows transition metals to form different oxidation states?
The similar energies of the 4s and 3d orbitals.
List some important oxidation states for Chromium (Cr).
- +3 in Cr2O3
- +6 in Na2Cr2O7 (orange), Na2CrO4 (yellow)
List some important oxidation states for Manganese (Mn).
- +2 in MnSO4
- +4 in MnO2
- +7 in KMnO4 (purple)
List some important oxidation states for Iron (Fe).
- +2 in FeCl2
- +3 in FeCl3
List some important oxidation states for Copper (Cu).
- +1 in CuI (white)
- +2 in CuSO4
What role do transition metals play in catalysis?
They are good catalysts.
Give examples of transition metals used as catalysts.
- Fe in the Haber process
- Ni in the hydrogenation of alkenes
- V2O5 in the contact process
- MnO2 in the decomposition of H2O2
What are the two types of catalysts?
- Homogeneous
- Heterogeneous
What is a homogeneous catalyst?
A catalyst in the same physical state as the reactions it catalyzes.
What is a heterogeneous catalyst?
A catalyst in a different physical state from the reactions it catalyzes.
What is a complex ion?
A metal ion surrounded by co-ordinately bonded ligands.
What is a ligand?
A small molecule or ion with a lone pair of electrons.
What is the geometry of a tetrahedral complex?
4 ligands arranged around the metal.
What is the geometry of an octahedral complex?
6 ligands arranged around the metal.
What does the complex ion [CoCl4]⁻ look like?
Blue
What does the complex ion [CuCl4]²⁻ look like?
Yellow/green
Provide an example of a complex ion and its color.
[Fe(H2O)6]²⁺ - pale green
Fill in the blank: A complex ion is a _______.
metal ion surrounded by co-ordinately bonded ligands.
What is the color of the complex ion [Cu(NH3)4(H2O)2]²⁺?
Royal blue
Reactions with hydroxide ions
Ligand exchange
When a transition metal ion is exposed to a mixture of ligands
the ligands can be exchanged to
form a new complex. This is an equilibrium process
e.g.
[Cu(H2O)6]2* + 4NHз = [Cu(NHз)4(H2O)2]* + 4H20
If more ammonia is added
the equilibrium shifts to the right
and giving a royal blue colour.
If more water is added
the equilibrium shifts to the left
pale blue colour.
Ligand exchange can lead to a change in geometry of the complex ion.
[Co(H2O)6]2* + 4Cl- = [CoCl4]2- + 6H2O
If a large amount of chloride is used
such as by adding concentrated hydrochloric acid
equilibrium shifts from the pink octahedral complex to the blue tetrahedral complex.
Transition metal ion
[Cr(H2O)6]3+
[Fe(H2O)6]2+
[Fe(H2O)6]3+
[Cu(H2O)6]2+
Addition of some OH-
Addition of excess OH
grey-green ppt of [Cr(H2O)з(OH)3] ppt dissolves giving a deep
green solution of [Cr(OH)6]3-
dark green ppt of [Fe(H2O)4(OH)2] no further reaction
red-brown ppt of [Fe(H2O)3(OH)3] no further reaction
pale blue ppt of [Cu(H2O)4(OH)2] no further reaction
- Form coloured complexes
Transition metal complexes are almost always coloured. However
in the absence of any ligands around the metal ion
Without ligands
a transition metal atom has five degenerate d orbitals
different to the other two. This splits the d orbitals to give two sets of orbitals close together in energy.
5 degenerate d-orbitals
2 d-orbitals
3 d-orbitals
ATOM
OCTAHEDRAL COMPLEX
Electrons in the lower 3d orbitals absorb energy from visible light
which promotes them to the higher 3d orbitals. Only one frequency (colour) of light is absorbed
between the orbitals. The rest of the frequencies are transmitted; hence
the complementary colour is observed. Compounds containing the complex [Cu(H2O)6]2* are typically blue as they absorb all
colours apart from blue.
Light absorbed of energy hf
OCTAHEDRAL COMPLEX
OCTAHEDRAL COMPLEX
The energy difference
AE
Copper(I) complexes have an electronic configuration with a full d sub-shell which means that there are no empty orbitals to allow electrons to move between energy levels
so copper(I) complexes
appear colourless.
