Why is the Ionization energy directly proportional to the penetrating power?

Answer 1

The penetrating power of an electron is its effective nuclear charge, or in simple terms how much is the total nuclear force between the electron and the atomic nucleus. If the probability of the electron present is closer to the nucleus, it will be held tightly by the nucleus and thus it will require more energy to knock that electron off. If it is farther away or at a lower penetration power it can be easily removed from the atom.the Ionization energy is the amount of energy required to remove the electron from an atom, thus the penetration power is directly proportional to the ionization energy.