(1) Samarium is a rare earth element, one of the elements that occupy the space in Row 6 of the periodic table between lanthanum and hafnium .(2) Gadolinium is a rare earth element, one of the elements that occurs in Row 6 of the periodic table between barium and hafnium .(3) Titanium is found in column four along with chemically similar zirconium, hafnium , and thorium.(4) In contrast with tungsten, hafnium does not interact readily with iron-rich material, but it does combine readily with the elements in rocks lacking in iron.(5) For most of history, hafnium and zirconium were not clearly distinguished from each other.
