You can plot ELF or LOL isosurface map to try to identify main occurrence region of valence shell electrons.

Another suggestion is plotting "valence electron density", as described in my paper http://www.whxb.pku.edu.cn/EN/10.3866/PKU.WHXB201709252. You can easily use Multiwfn to plot this kind of map, see Section 4.6.2 of Multiwfn manual for example, what you need to do is setting occupation number of inner-core MOs to zero and then plot electron density map as usual.

Hi there, I am currently studying the difference in electronic structure of carbenes. Suppose, there are three species, singlet and triplet CH2, and CH3 radical. How can I distinguish the location of the valence shell electron of these species?