Question

In the 19th century, Dmitri Mendeleev predicted the existent of a then unknown element, X, with a mass of 68. He also predicted that an oxide of X would have the formula X2O3, on the modern period table. What is the group number and period of the element?

Answer 1

Base on your question that in 19th century when Dmitri Mendeleev predicted the existent of an unknown element X with a mass of 68 and he also predicted that an oxide would have a formula X203 on the modern table i think the element that Mendeleev predicted is (GA) Gallium