Transision elements Flashcards
What makes an element a transition metal?
They have partially filled d subshells as atoms or ions
What elements in the d-block have full d subshells?
Zinc, Cadmium and mercury
Form 2+ ions by losing electrons in the 4s subshell, leaving the 3d full
Why can transition metals have multiple oxidation states?
The first ionisation energies are close together, so one or all the electrons could be removed
What is coordination number?
Total number of points at which a central atom or ion attaches ligands
Coordination sphere
The region surrounding the central atom/ion with the ligands
Shape of complex ion with coordination number 6
Octahedral
When is a complex ion with coordination number 4 tetrahedral?
When electrons are spin free
When is a complex ion with coordination number 4 square planar?
When electrons are spin paired
Shape of complex ion with coordiantion number 2?
Linear
Bidentate ligand
Ligand with two lone pairs that can bond to the central atom
Why are paired electrons in an orbital at a higher energy than those in singly occupied orbitals?
Due to the repulsion, more energy is needed to maintain this arrangement
What needs to be absorbed in order to see a colour and why?
The colour of the opposite wavelength on the colour wheel, as the other colours will cancel out
What causes the d sub-level in transition metal to split?
Ligands form dative bonds with two of the orbitals.
The electrons in these orbitals repel the electrons in the ligands
These orbitals move to a higher energy level to maintain this position
Why do transition metals form coloured compounds?
When the d sub-level is split, electrons move between the two energy levels.
When electrons are promoted, they absorb light of a specific wavelength and the opposite wavelength is observed.
Most important factor affecting crystal field splitting energy (Δo)
Splitting strength of ligands
How does size of atom affect Δo ?
The bigger the atom, the more electrons in the d orbital. Δo increases due to more orbital overlap
How does oxidation state affect Δo?
The higher the oxidation state (charge), the closer the ligands are. More repulsion in the orbitals, so greater orbital split
What is crystal field splitting energy?
The difference in energy between the two split sub-levels
What is spin?
The tendency of electrons to move away from each other
Why do high energy splits have a spin paired arrangement?
It is too far for the electron to be permanently elevated to a higher level. More energetically favourable for the electron to remain paired.
energy of split > energy of spin
Why do low energy splits have a spin free arrangement?
It is close enough and energetically favourable for the electron to be permanently elevated to a higher level.
energy of spin > energy of split
