Examples include lutetium, europium, samarium and neodymium.
One member of this set has a namesake "anomaly" because it is so readily absorbed in plagioclase that it is either very enriched or depleted. Another of them forms, with iron and boron, the strongest known magnets. All of them are trivalent, and this class of (*) elements displays a namesake contraction. Examples include lutetium, europium, samarium and neodymium. For 10 points, identify this set of elements, defined by their filling of the 4f subshell, one row above the actinides.
One member of this set has a namesake "anomaly" because it is so readily absorbed in plagioclase that it is either very enriched or depleted.
lanthanides [or lanthanoids]