Atomic number of Arsenic is 33. And the electronic configuration of Arsenic is [Ar] 3d10 4s2 4p3.
Now, valence electrons are the electrons present in outermost shell. With reference to Arsenic, valence shell is n = 4. And in 4th shell, there are no electrons present in d-orbital.
On other hand, 3rd shell is not the valence shell in case of Arsenic. Hence, electrons present of 3d shell of Arsenic cannot be referred as valence electrons.