Question about basic chem

[EugeneChien]

Say if you have an ion that is isoelectronic with one of the exceptions ( Cu or Cr ), such as Co 2-, would the electronic config be [AR] 4s1 3d10 or 4s2 3d9 ? thanks for any help in advance.

 

[miniMUNCH]

I'm thinking Co 2- would be 3d10 4s1 as it is the preferred configuration for Cu (29 electrons)...but electrons in Co 2- and Cu are not equivalent in energy, etc. because the Co/Cu nuclei have different number of protons and thus exhibit a different attractive force on electrons which, in turn, could results in significantly different electronic structures.

I don't know of any reliable rules of thumb to apply to the entire periodic table of elements in this regard. Pretty much have to make an educated guess from surrounding element electronic structures or look it up or calculate it using quantum mechanics (density functional theory DFT).