镧系元素的许多性质都能随原子序数的增大而表现出某种规律性的变化。深入地研究这种变化规律,不但能够指导人们提高稀土生产的工艺技术水平,而且将推动化学键、原子结构等重大理论问题的发展。正因为这样,它一直是引人注目的一个研究课题。最直观、也是人们最熟悉的一条规律是从镧到镥,原子量依次增大,以此为依据,结合其它各种性质,人们将镧系元素分成轻镧系和重镧系两大组(有时也将其分成轻镧系中镧系 Many properties of lanthanides can exhibit some regular changes with the increase of atomic number. In-depth study of this change, not only can guide people to improve the level of production technology of rare earths, but also promote chemical bonds, atomic structure and other major theoretical issues. Because of this, it has always been an attractive research topic. The most direct and familiar rule is that from lanthanum to neptunium, atomic weight increases in turn, based on which, in combination with other various properties, lanthanides are divided into two groups, lanthanides and lanthanides (sometimes It is also divided into light lanthanide lanthanides