The correct answer to the question is from outer region or the valence shell.
EXPLANATION:
As per the question, the atomic number of the element Z = 13.
The mass number of the element A = 27
The element whose atomic number 13 and mass number 27 corresponds to Aluminium.
The electronic configuration of Aluminium is [tex]1s^22s^22p^63s^3[/tex].
Hence, the valence shell of the Aluminium i.e M- shell contains three electrons.
The electrons present in the valence shell are loosely bound to the nucleus. These electrons can be easily escaped from the outer shell when they are excited by providing a little bit of energy from any external source. The innermost electrons are tightly bound to the nucleus.
As per the question, three electrons are lost from the neutral atom of Aluminium. These three electrons are lost from the valence shell or the outer region of the atom as they are loosely bound to the nucleus.
