I would kindly appreciate an explanation in terms of the two accepted quantum mechanical theories -valence bond & molecular orbitals- for the electronic energy level structure in natrium fluoride $\ce{NaF}$.
I read here that from a non-quantum perspective the $\text{3s}$ electron of $\ce{Na}$ "jumps" to join the $7$ electrons of the $\text{2p}$ level of $\ce{F}$. This way, the $\text{Na}$ atom becomes the $\ce{Na+}$ ion, while the $\ce{F}$ atom becomes the $\ce{F-}$ ion. All nice until now but handwaving, or high-school level if you prefer.
So how is then the $\ce{Na-F}$ bond (thus the molecule) defined in terms of the electronic wavefunctions of the two original atoms?
How is this generalized to $\ce{MgF2}$ to explain a bond angle of 180 degrees (is this right?)? What about the crystal structure explained quantum mechanically?
Sorry if I ask too much in one shot.