Understanding electronic configurations is vital, but a huge number of students face difficulties in understanding the why and the how. What approach do you think I should take in explaining electronic configurations to a student who only knows the Bohr model? Thanks.
As an undergrad student that has recently learnt that the Bohr model is just an approximation at best, and mostly incorrect, I think I am well equipped to answer this.
When I first learnt about the structure of an atom, I was told that "electrons move around the nucleus in fixed paths having fixed energy, called orbits. The angular momentum of the electrons is an integer multiple of $h/2\pi$."
When I was first taught the electronic configurations and the quantum mechanical structure of an atom, my teacher explained it thus (and it was easily understood by most of the class): he made an analogy between a person's location and the location of an electronic.
Just how a person can be located if we know which country they're in, which city they're in, which locality, which room, and finally which area in the room; an electron can be approximately located if we know its principal quantum number, its azimuthal quantum number and its magnetic quantum number. Another quantum number, i.e., spin quantum number tells us which direction it is spinning in.
After this, a brief historical understanding of why the Bohr model was discarded and this model was proposed was given to us. The Heisenberg's uncertainty principle, and the Schrodinger equation were introduced, as the uncertainty principle explained why Bohr's model was incorrect, and the Schrodinger equation explained how to find the probability density of the presence of the electron.
This method helped me understand as it felt like I was transitioning through the same phases that all the people of the scientific community had to when the quantum mechanical model was on its way in, and the Bohr model on its way out. This really felt like a fluid transition, rather than "Bohr was wrong, this is right", which would've caused a lot of confusion (at least for me).
Finally, there isn't a one size fits all answer to this, as every student is different. I am just sharing my experience.