1. Peter Irks Rhea. Commits Critical Felony. Felony committed at Night is Minimum.
2. Cold Condition. (say) NO 2 Night Halting (for 3 Hrs). Non-Committed-Souls Head 2 Office. Office Hours For Super-Committed-Nerds Closes Before.
In a crystal field the d-orbitals of the metal ions gain degeneracy due to Ligand electrons. (That is the equal energy levels of d-orbitals of metal are now unequal due to electron repulsion from Ligand, depending on in which direction the d-orbitals are pointed to Ligand)
Which ions (or Ligands) are more powerfully degenerated (or degenerative) and which are less? There is an order called Spectro-Chemical series.
So I just thought a little to easily remember the series.
1. When geometry (eg tetrahedral or octahedral) and Ligands are fixed how does it affect the metal ions? More splitting denoted by >.
(strong field) Pt4+ > Ir3+ > Rh3+ > Co3+ > Cr3+ > Fe3+ > Fe2+ > Co2+ > Ni2+ > Mn2+ (weak field)
2. When geometry and metal ions are fixed how are Ligands affecting?
CO (~) CN- > NO2- > NH3 > NCS- > H2O > OH- > F- > SCN- (~) Cl- > Br-
The concept behind Crystal Field Theory (Incidentally developed by Physicists like Hans Bethe as an alternative to Valence Bond theory) is described in detail here.
M Dash Foundation: C Cube Learning 
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