Why is more energy required to remove an inner shell electron than a valence electron from an atom?
Electrons are attracted to the positive charge on the nucleus. The further an electron is found from the nucleus of an atom, the lower the force of attraction between it and the nucleus. Therefore an electron far away from the nucleus (like a valence electron) will have less of an attraction to the nucleus than one close to it. A lower attraction to the nucleus translates into the fact that less energy would then be required to remove the electron from the vicinity of that nucleus.
