已发现的各种稀土元素都属门捷列夫周期表上的第三组。它们大多都具有共同的化学特性和物理特性,但同时又都具有各不相同的性质。对若干种稀土元素,例如对钕、镧或铈等,已进行过许多的研究和试验,并已广泛地在工业上应用了。而其它一些元素目前还是一些稀见的元素,它们的特 The various rare earth elements that have been discovered belong to the third group on the Mendeleev’s periodic table. Most of them share common chemical and physical properties, but at the same time they all have different properties. Many kinds of rare earth elements, such as neodymium, lanthanum or cerium, have been studied and tested in many fields and have been widely used industrially. While some other elements are still some rare elements, their special