1) Which complex ion should have the largest crystal field division, delta? Explain why?
1) The aquatic complex will have the highest separation energy of the crystal field. Indeed, water is a stronger field ligand than chloride. As to why, I’m not really sure, but I think the general trend is that stronger Lewis bases are stronger field ligands – so poor bases like Cl- are weak, while stronger bases strong as NH3 are strong field. There are also other factors that influence these ratings – backbonding by multi-bonded binders (CO and CN being examples) makes these field binders very strong. These classifications are called spectrochemical series.
2) because [Cr(H2O)6]3+ has a larger gap between its two energy levels (this is the splitting energy of the crystal field), the transitions between t2g levels and for example for this complex will require more energy and therefore photons of wavelength shorter than for [CrCl6]3-.
Source(s): http://en.wikipedia.org/wiki/Crystal_field_theory
http://en.wikipedia.org/wiki/Spectrochemical_serie…