Chemistry of D-block
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What is the d-block?
The groups of elements whose outer electrons are found in d-orbitals.
What is a transition element?
A metal that possesses a partially filled d sub-shell in its atom or stable ions.
Which element in the d-block is not considered a transition element?
Zinc, as it has a filled d sub-shell and maintains this in its compounds.
What is the order of filling electron orbitals for d-block elements?
Fill 4s, then 3d then 4p.
Which elements in the d-block do not obey the electron filling rules?
Chromium and Copper as they each have one electron in the 4s orbital, leading to a more stable configuration since shells are more stable if they are filled or half-filled.
How are electrons lost when forming d-block ions?
4s electrons are lost first because 4s and 3d energy levels are close together so it is more energetically favourable to lose the 4s electrons before the 3d electrons.
What do the oxidation states of the d-block elements look like?
They have a large range of oxidation states because the energies of the 4s and 3d orbital are very close together, so it takes a similar amount of energy to remove any of these electrons.
What happens when the transition metals form compounds?
Energy is released, either through the formation of covalent bonds or when an ionic lattice is formed,
What does the oxidation state of each transition metal depend on?
Many factors, such as the oxidising power of the other atoms in the compounds.
How do transition metals form bonds with ligands?
The metal has an empty orbital and the ligand has a lone pair The two atomic orbitals overlap to form a molecular orbital A coordinate bond is formed
What is a ligand?
A small molecule with a lone pair which can form a bond to a transition metal.
Give examples of ligands
H2O, NH3, Cl- and CN-
What is a complex?
A combination of the transition metal ion and the ligands.
What are the two shapes transition metal complexes can possess?
Six ligands arranged octahedrally around the metal atom (most common) Four ligands arranged tetrahedrally around the metal atom (less common)
What factors influence the shape of the complex?
The metal The oxidation state of the metal and the ligands
Describe the shape of [Cu(H2O)6]2+ and [Co(H2O)6]2+
Present in most aqueous solutions of Cr2+ and Co2+. Octahedral shape with one lone pair on each oxygen atom of the H2O bonded to the metal.
Describe the shape of [Cu(Nh3)4(H2O)2]2+
Addition of ammonia to a solution containing [Cu(H2O)6]2+ causes four ammonia molecules to replace water molecules creating a royal blue octahedral complex which has two arrangements. In the trans isomer, the two water molecules are opposite each other (most common). In the cis isomer, the two water molecules are next to each other.
Describe the shape of [CuCl4]2- and [CoCl4]2-
Tetrahedral complexes formed when copper(II) or cobalt (II) ions react with concentrated HCL which displaces the water molecules.
What colour change occurs when forming [CuCl4]2- and [CoCl4]2-?
Copper (II) goes from pale blue to yellow/green Cobalt (II) goes from pink to blue
What happens when a transition metal ion is exposed to a mixture of ligands?
The ligands can be exchanged to form new complexes in an equilibrium process.
How can we view LeChateliers principle with transition metals?
There could be a colour change or a change in coordinate geometry.
Are transition metals coloured?
No, only their complexes are coloured due to the ligands having a dramatic effect of the orbitals in the metal atom.
What are the five degenerate d-orbitals for metal atoms?
dxz dxy dyz dx2-y2 dz2
How does the presence of ligands affect the orbital shape of the transition metal?
The ligands approach the transition ion along the directions of the three axes. Their negative charges repel the electrons in the orbitals that point along these axes, which makes the orbitals less stable. The orbitals that do not point along the axes are not made less stable. So the overall energies of the orbitals is not the same.