While reading applications of coordination compounds, I read that Hardness of water can be checked using Na2EDTA in hard water containing Ca+2 and Mg+2 which form complexes with EDTA.

Also, Lead (Pb), a p block element is removed by using EDTA in case of lead poisoning.

Can elements other than those of d block form complex compounds? Like Ca(II) or Mg(II). How are such complexes stable? Can we desrcibe crystal splitting in them?

  • $\begingroup$ I know there are elements not from the d-block that can form coordination complexes. I don't remember exactly which ones (maybe the bigger ones, block p like Al (III), maybe Tl (I), etc., not sure if someones of group II). My initial guess for describing crystal splitting: depends, generally dissolved in water, must consider hydration enthalpy change and lattice energy breaking, etc. $\endgroup$
    – Orr22
    Jan 13, 2016 at 12:11
  • $\begingroup$ But which orbitals will split? np orbitals? $\endgroup$
    – Quark
    Jan 13, 2016 at 12:13
  • $\begingroup$ Not sure, that will depend on the theory that describes the orbital overlap: more calssical CFT (en.wikipedia.org/wiki/Crystal_field_theory) or more quantum- orbital molecular LFT (en.wikipedia.org/wiki/Ligand_field_theory). Elements from 4th period and after [maybe Tl (I, III)?] may have p-d overlaping, thus allowing coordination. $\endgroup$
    – Orr22
    Jan 13, 2016 at 12:19
  • $\begingroup$ Most of the transition metal form edta complex. See: pubs.acs.org/doi/abs/10.1021/jp904296m $\endgroup$ Nov 30, 2020 at 6:22


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