Why does it take much more energy to ionize an electron when it is in the ground state then when it is in an excited state?

Ionizing an electron from the ground state requires more energy because it is more tightly bound to the nucleus due to lower energy levels. In contrast, an electron in an excited state has absorbed energy and occupies a higher energy level, making it less tightly bound and easier to remove. As a result, the energy required to overcome the attractive force of the nucleus is greater for ground state electrons compared to those in excited states.