Explain in brief the factors influencing the ionisation energy of elements in the periodic table

Factors influencing the ionisation energy of elements in the periodic table
The charge on the nucleus – The ionization energy increases with the increase in the nuclear charge. More is the number of protons in the nucleus, more positively charged the nucleus is and the more strongly electrons are attracted to it.
The distance of the electron from the nucleus- Ionization energy decreases with the increase in the distance between nucleus and valence electron. Nuclear attraction falls off very rapidly with distance. An electron close to the nucleus will be much more strongly attracted than one further away. Thus, ionisation energy decreases with increase in size and increase with decrease in size of an atom.
The number of electrons between the outer electrons and the nucleus – The inner electrons present in shells between nucleus and valence shell reduce the attraction between nucleus and the outermost electrons. More is the screening of outer electrons forms inner electrons, less is the nuclear pull on outer electrons and thus less is the ionization energy.
Penetration effect- Thus Ionisation energy to remove an electron from a given energy level decreases in order s > p > d > f.
Electronic configuration- Atoms having stable configuration (i.e. fully filled or half filled) have least tendency to lose electron and hence have high value of ionization enrgy.


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