The effective nuclear charge is the net positive chargeexperienced by an electron in a multi-electron atom.The term "effective" is used because the shieldingeffect of negatively charged electrons prevents higherorbital electrons from experiencing the full nuclearcharge by the repelling effect of inner-layer electrons.The effective nuclear charge experienced by the outershell electron is also called the core charge. It is possibleto determine the strength of the nuclear charge bylooking at the oxidation number of the atom