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1871年,门捷列夫在他的周期律的基础上曾预言有第21号元素存在,这个元素是金属,直到1879年尼尔松才从斯堪的纳维亚(Scandinavia)半岛的矿样中离析出
In 1871, Mendeleev predicted on the basis of his periodic law the presence of element no. 21, a metal that was found only from ore samples of the Scandinavia peninsula in 1879 In the isolated