Transition elements

Transition element is a d-block element that forms one or more stable ions with an incomplete d subshell

Sc: 4s2 3d1

Sc^3+/[Ar]: 4s0 3d0, Therefore Sc is not a transition element as it has no d subshell

Zn: 4s2 3d10

Zn^2+: 4s0 3d10, Therefore Zn is not a transition element as it has a complete d subshell

Shapes of orbital

If the orbital is found not on the axis, read as alphabetical order

If the orbital is found on the axis, read as Xsquare - Ysquare

dXY

Ligand is a species that contains a lone pair of electrons that forms a dative bond to a central metal atom/ion
Complex is a molecule or ion formed by a central atom/ion surrounded by one or more ligands
Co-ordination number is the number of co-ordinate bonds to the central metal ion

One co-ordinate bond

Ex: ammonia, water, Cl- and CN-

Two co-ordinate bonds

Ex: 1,2-diaminoethane -NH2CH2CH2NH2 (en) Ethanedioate ion, C2O4 2-

More than two co-ordinate bonds

Ex: EDTA 4-

Colour changes arises because different ligands causes the d orbitals to split by a different amount of energy according to their coordinate number
Different colour is absorbed from the visible light and complementary colour is seen and with the formula of E=hf as h being the planack constant, we can caluculate the frequency of the light spectrum and identify which light is absorbed.
• Part of the visible spectrum is absorbed by the transition metal complex
5 d orbitals in transition metals or ions are described as degenerate, same energy level
The coordinate bonding with the ligands causes the orbitals to split into two sets of non-degenerate orbitals which has varying energy levels

In octahedral complexes, they are six ligands arranged around the central metal ion
The lone pair of electron of the ligands repel the electrons in the x^2-y^2 and z^2 orbitals of the metal ion more than they repel the electrons in the 3dyz, 3dxz and 3dxy orbitals
This is because the 3dx^2-y^2 and 3dz^2 orbitals line up with the dative bond in the complex's octahedral shape
This is because the ligands are attached to or approaching the central metal ion along the X Y and Z axes, and the 3dx^2-y^2 and 3dz^2 orbitals have lobes around the axes.
The electrons in these two orbitals are closer to the bonding electron, so there is more repulsion
This means that when the degenerate d orbital split, the 3dx^2-y^2 and 3dz^2 orbital are at a slightly higher energy level than the other three
The difference in energy between the non-degenerate d orbitals is labelled as E.
d-d transition occurs and excited electron goes to the higher level orbital and absorbs energy
Energy absorbed has a specific frequency that is found in a specific colour of light

In tetrahedral complexes, there are four ligand attached to the central metal ion
The bonding pair of electrons from the four ligands now line up with the 3dxz, 3dxy and 3dyz orbitals of the central metal ion
Now the 3dx^2-y^2 and 3dz^2 orbitals lie between the ligands
Thus, there is less repulsion with the 3dx^2-y^2 and 3dz^2 orbitals
When the degenerate orbital split, the 3dx^2-y^2 and 3dz^2 orbitals are at a lower and more stable energy level that the other three
d-d transition occurs and excited electron goes to the Lower level orbital and absorbs energy
Energy absorbed has a specific frequency that is found in a specific colour of light