Why is it harder to remove an inner shell electron than a valence electron from an atom

I should think because the valence bonds want to escape and bond more whereas the inner layers are for the most part stable

They're closer to the nucleiionization energy is higher. having inner shells and a valence only means that the inner shells are conpletely filled and stable.
valence electrons are easily removed only if the number of electrons is =<3 otherwise, they gain rlectrons.

Ci think not