so I put it in this way- I have read in that we can't isolate an atom like to find its radius. like, hey, come here alone, lil guy, I have to measure your radius. We always measure the distance between two nuclei of two atoms and divide the it by 2.
on the other hand, in wave functions we take two or more isolated independent atoms.
Ψa- atom a Ψb- atom b
so my question is when we can get an atom isolated then why can't we take out its radius without having it been bonded (covalent, metallic and ionic)?