Question

Why can we not figure out the number of valence electrons in transition metals?

Please help... Thanks!

Answer 1

It is due to the `(n-1)d` and `ns` orbitals being fairly close in energy to each other, usually allowing access of electrons from both sets of orbitals when bonding.

I go into detail on this here:
https://socratic.org/s/aMJvqHfH