Difference Between Shielding and Screening Effect

Key Difference – Shielding vs Screening Effect
 

The shielding effect is the reduction in the effective nuclear charge on the electron cloud, due to a difference in the attraction forces of the electrons in the nucleus. In other words, it is the reduction of attraction between the atomic nucleus and outermost electrons due to the presence of inner shell electrons. The terms shielding effect and screening effect mean the same. There is no difference between shielding effect and screening effect.

CONTENTS

1. Overview and Key Difference
2. What is Shielding Effect
3. What is Screening Effect
4. Shielding vs Screening Effect
5. Summary

What is Shielding Effect?

Shielding effect is the reduction in the effective nuclear charge on the electron cloud, due to differences in the attraction forces between electrons and the nucleus. This term describes the attraction forces between electrons and nucleus of an atom having more than one electron. It is also called atomic shielding.

The shielding effect gives the reduction of attraction between the atomic nucleus and the outermost electrons in an atom containing many electrons. The effective nuclear charge is the net positive charge experienced by the electrons in the outermost electron shells of an atom (valence electrons). When there are many inner shell electrons present, the atomic nucleus has less attraction from the atomic nucleus. That is because the atomic nucleus is shielded by the electrons. Higher the number of inner electrons, greater the shielding effect. The order of increasing the shielding effect is as follows.

S orbital>p orbital>d orbital>f orbital

There are periodic trends of shielding effect. A hydrogen atom is the smallest atom in which one electron is present. There are no shielding electrons, therefore the effective nuclear charge on this electron is not reduced. Hence, there is no shielding effect. But when moving across a period (from left to right) in the periodic table, the number of electrons present in the atom increases. Then the shielding effect is also increased.

The ionization energy of atoms is determined mainly by the shielding effect. Ionization energy is the amount of energy required to remove the outermost electron from an atom or an ion. If the shielding effect is high, then the outermost electron of that atom is less attracted to the atomic nucleus, in other words, the outermost electrons is easily removed. Hence, greater the shielding effect, lesser the ionization energy.

However, there are some exceptions of ionization energy values when moving across a period of the periodic table. For example, the ionization energy of Mg (Magnesium) is higher than that of Al (Aluminum). But the number of electrons in Al is higher than that of Mg. This happens because the Al atom has the outermost electron in a 3p orbital and this electron is unpaired. This electron is shielded by two 3s electrons. In Mg the outermost electrons are two 3s electrons that are paired in the same orbital. Therefore, the effective nuclear charge on the valence electron of Al is less than that of Mg. Therefore it is easy to be removed from Al atom, resulting in a less ionization energy compared to Mg.

What is Screening Effect?

The screening effect is also known as the shielding effect. It is the effect of reduction of attraction between the atomic nucleus and outermost electrons due to the presence of inner shell electrons. That occurs because the inner shell electrons shield the atomic nucleus.

What is the Difference Between Shielding and Screening Effect

• Shielding effect is the reduction in the effective nuclear charge on the electron cloud, due to differences in the attraction forces between electrons and the nucleus. Shielding effect is also known as the Screening Effect. Hence, there is no difference between these two terms. They primarily mean the same thing.

Summary

The shielding effect or screening effect is the reduction of attraction between the atomic nucleus and outermost electrons due to the presence of inner shell electrons. The shielding effect causes the reduction of effective nuclear charge on an electron. The valence electrons are affected by this effect. There is no difference between the terms shielding effect and careening effect.

Reference:

1.“6.17: Electron Shielding.” Chemistry LibreTexts, Libretexts, 23 Aug. 2017. Available here
2.“Shielding Effect.” Shielding Effect | Definition | Trend | TutorVista. Available here 
3.“Shielding effect.” Wikipedia, Wikimedia Foundation, 5 Mar. 2018. Available here   

Image Courtesy:

1.’Effective nuclear charge diagram’By FrozenMan (Public Domain) via Commons Wikimedia