Effective atomic number, denoted by ''Z''
eff, may refer to:
*
Effective nuclear charge In atomic physics, the effective nuclear charge is the actual amount of positive (nuclear) charge experienced by an electron in a multi-electron atom. The term "effective" is used because the shielding effect of negatively charged electrons preven ...
of an individual atom, as felt by electrons within that atom
*
Effective atomic number (compounds and mixtures) of a composite material
{{disambiguation