transition element

transition-element的词性：
n.（名词）

1. Any of the metallic elements that have an incomplete inner electron shell and that serve as transitional links between the most and the least electropositive in a series of elements. They are characterized by multiple valences, colored compounds, and the ability to form stable complex ions.
过渡元素：任一种不完整的内部原子壳层，并在一系列正电性的最强和最弱元素中起过渡联系作用的金属元素。它们呈现多种原子价，包括有色化合物，有构成稳定复杂离子的能力