The energy necessary to overcome the attractions of electrons to the nucleus of an atom so as to remove electrons from the atom is called electron energy charging energy electrical energy ionization energy

Option-(D): Ionization energy

The energy necessary to overcome the attractions of electrons to the nucleus of an atom so as to remove electrons from the atom is called the  ionization energy.

There is always a requirement for having some changes inside the electronic configuration of the different elements or more over the atoms, as the elements are targeted by the external source of energy in order to raise its loosely bounded electrons to such an extent that they get away from the force,F of attraction of the atoms nucleus. And, that is why we say that when an atom loses or gains an extra charge particle it is then termed as the Ion or the molecules as whole is in the ionized form or state.So, we can just say that the amount of energy,E which is required to ionize any molecule or atom is called the ionization energy,E(ionization).

Because a model would make the investigation easier to understand