what is screening effect

Hello student
A valence-electron in a multi-electron atom is attracted by the nucleus, and repelled by the electrons of inner-shells. The combined effect of this attractive and repulsive force acting on the valence-electron experiences less attraction from the nucleus. This is called shielding or screening effect. The magnitude of the screening effect depends upon the number of inner electrons,i.e.,higher the number of inner electrons, greater shall be the value of screening effect.

It is described as a decrease in shielding effort between the nucleus and last orbital due to electrons present between them i.e., greater the screening effect, easier the removal of electron. In solids, especially in metals and semiconductors, the electrostatic screening or screening effect reduces the electrostatic field and Coulomb potential of an ion inside the solid. Like the electric field of the nucleus is reduced inside an atom or ion due to the shielding effect, the electric fields of ions in conducting solids are further reduced by the cloud of conduction electrons.
The shielding effect describes the attraction between an electron and the nucleus in any atom with more than one electron shell.