a bivalent and trivalent metallic element of the rare earth group
造句
用作名詞(n.)
The lighter rare-earth metals, from cerium to europium in the first half of the series, have more complex crystal structures than the heavier elements. 輕的稀土金屬，從鈰到銪的前一半序列比重元素具有更為復雜的晶體結構。