Shielding (atomic physics)
Shielding designated in an electron  atom the reduction of the attractive interaction between an electron and the nucleus by the action of other electrons. In the central field model of the atom, the energy of an electron depends on the quantum numbers and :
With
 effective atomic number
 Atomic number
 Shielding constant (see below)

effective quantum number (see below)
 Principal quantum number
 Quantum defect
 Rydberg energy (there also the formula for oneelectron systems for comparison ).
For the radial parts of the associated oneelectron wave functions , John C. Slater proposed the following analytical expression:
with the normalization factor N.
Oneelectron wave functions with radial components determined in this way are called Slater orbitals .
Slater rules
The shielding constant and the effective quantum number are determined as follows:
 Electron shells with principal quantum numbers greater than n are not taken into account.
 Each additional electron with the same n contributes 0.35 (but only 0.3 for n = 1).
 Each electron in shell n  1 contributes to :
 for secondary quantum numbers l = 0 (s subshell) and l = 1 (p subshell): 0.85 each
 for secondary quantum numbers l = 2 (d subshell) and l = 3 (f subshell): 1.0 each.
 4. All electrons from even deeper shells make a contribution of 1.0.
The following table follows:
n  1  2  3  4th  5  6th 

n '  1.0  2.0  3.0  3.7  4.0  4.2 
To the quantum defect .
impact
As part of the Sommerfeld atomic model, the orbital degeneration , i.e. the energy equality of states of the same principal quantum number n but different angular momentum quantum number l, is eliminated by the shielding, since the orbits of different angular momentum quantum numbers are subject to different shields.
Web links
 Shielding for spectrum, lexicon of physics