Protons and Neutrons comprise the nucleus of the atom. If the balance or stability of the atom is changed by the removal or addition of an electron or a proton, the atom becomes a charged entity called an ion. In nature, all atoms seek their lowest energy state or, in other words, seek to return to stability. This is fundamental to the production of x-rays or photons. In doing so, a series of events may occur.
Electrons orbit the nucleus in a series of shells or energy levels.
Those shells closest to the nucleus therefore are highest in binding energy while those levels furthest from the nucleus have less. It is important to note and remember that this binding energy is negative energy. In order to remove an electron from its orbit, one needs an energy equal to or greater than its binding energy. It is also important to remember that though an atom is a minute structure, the space between each electron is immense in proportion to the mass of each particle. A K shell electron with a binding energy of 69.5 KeV is removed.