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稀土或钢系元素是指元素周期表中ⅢB族内原子序数由57～71的1j种金属。其中14种金属是自然存在的,锚是原予核分裂反应的不稳定产物。由于钇与稀土的化学相似性并通常与稀土共存,虽然其原子序数是39,亦包括在这一族中。所有稀土金属均有银灰色的光泽,在空气中会迅速氧化而形成稀土氧化物尺1 0。。通常随着原子序数的增加,密度(除铕、镱外)、原F量、硬度均提高,而韧性降低。
Rare earths or elements of the steel system refer to the metals of Group 1i of atomic numbers 57 to 71 in Group IIIB of the Periodic Table. Fourteen of these metals are naturally occurring and anchors are unstable products of the original mitotic response. Due to the chemical similarity of yttrium to rare earths and their coexistence with rare earths, their atomic number is 39 and is also included in this family. All rare earth metals have a silver-gray luster, the rapid oxidation in the air to form a rare earth oxide ruler 10. . Usually with the atomic number increases, the density (except europium, ytterbium outside), the original amount of F, hardness are increased, while reducing the toughness.