Definition Consider the third electron in a lithium atom.
However it is also repelled by the charge on the inner two electrons. Electrons in the 1s orbital are much closer to the nucleus than any electrons in the 2 s or 2 p orbital. The difference between the full nuclear charge, Z , and the screening effect of the inner two electrons is called the effective nuclear charge, or Z eff . In general, for any many-electron atom, any particular electron will always be screened from the nucleus to some extent by the remaining electrons. 5d 6s 6p Literature sources E. Clementi and D.L.Raimondi, J. Chem.