The
effective nuclear charge (often symbolized as or ) is the net positive charge experienced by an
electron in a multi-electron
atom. The term "effective" is used because the
shielding effect of negatively charged electrons prevents higher orbital electrons from experiencing the full
nuclear charge by the repelling effect of inner-layer electrons. The effective nuclear charge experienced by the outer shell electron is also called the
core charge. It is possible to determine the strength of the nuclear charge by the oxidation number of the atom.