What is the shielding effect in atoms?

The screening effect, or shielding effect, is how electrons in the same atom interact with each other. In a single-electron atom (in isolation), the electron is only interacting with the proton; in a multielectron atom, the electrons are both interacting with the proton(s), but also with each other. While electrons are attracted to the protons in the nucleus, they are repelled by the other electrons. This electron-electron repulsion decreases the attractive force of the protons on the electrons.

The shielding effect changes the effective nuclear charge -- effectively decreasing the true nuclear charge. This effect causes atoms to get smaller as you across a period (row) of the periodic table, as well as many other periodic trends observed in the periodic table.

See the Web Links and Related Questions for more information about shielding and periodic trends.

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keep in mind that different orbitals have varying shielding effciencies depending on their shape and symmetry

from greatest effect to least

s>p>d>f

and the effective nuclear charge can be estimated with good approx. by the Slater's Rule

where

Z_eff=Z-S

Z_eff= effective nuclear charge Z=nuclear charge S=screening (or shielding) factor

the screening factor is calculated by following the directions given at this website

http://intro.chem.okstate.edu/WorkshopFolder/SlaterRule.html