Source: wikibot/lanthanide-contraction
= Lanthanide contraction
{wiki=Lanthanide_contraction}
Lanthanide contraction refers to the phenomenon where the atomic and ionic radii of the lanthanide series elements (the 15 elements from lanthanum (La) to lutetium (Lu) in the periodic table) decrease progressively with increasing atomic number, despite the addition of electrons to the 4f subshell. This contraction is primarily caused by the ineffective shielding of the increasing nuclear charge by the 4f electrons.