Mendeleev completed the first periodic table of chemical elements in the world in 1869, including all 63 known elements at that time arranged into different families in accordance with atomic weight. In addition, he reserved some vacancies and predicted
the existence of some unknown elements and their characters. In the following decades, these vacancies had been successively filled up by newfound elements. In 1877, Guo Songtao, the first Chinese envoy to Britain, heard the story about Mendeleev’s prediction and
the discovery of element Gallium, associating with the course of discovery of Neptune, he unfeignedly praised the western sciences in
terms of delicacy and efficacy.