So the hexaaquacopper (II) ion has an octahedral structure with 6 aqua ligands datively bonded to the central Cu2+ cation:

A hexaaquacopper (II) ion

My question is: how is this possible if the electronic configuration of the Cu2+ cation is [Ar]4s-0 3d-9. This only leaves one empty 4s orbital and 3 4p orbitals available for dative bonding which would suggest that a tetraaqua complex should form but this is not the case?

  • $\begingroup$ 4d is participating. $\endgroup$ Jan 29, 2018 at 18:24
  • $\begingroup$ How is this possible? Wouldn't the 4d be at too high of a level to participate? $\endgroup$ Jan 29, 2018 at 18:44
  • $\begingroup$ @WeijunZhou It's not. OP's right. $\endgroup$
    – Mithoron
    Jan 29, 2018 at 18:59
  • $\begingroup$ @Mithoron This is from a highly phenomenological description that describes the central atom as undergoing $sp^3d^2$ hybridization (as in this figure which contains Chinese: $sp^3d^2$ for Fe and that is what I have been taught years ago. I know that CFT and LFT are far better alternatives and I should be more careful next time in making comments. $\endgroup$ Jan 29, 2018 at 19:03
  • $\begingroup$ @LemuelCrentsil The link above already pretty much answers your question, but you may wish to also learn about the alternative theory as listed here, which is still quite commonly used in some elementary courses. It's simple to understand, but not correct, and resulted in my comment above. You should always use CFT or LFT whenever possible. $\endgroup$ Jan 29, 2018 at 19:12