"Despite Mendeleev's initial system being flawed, and the correct theoretical basis of the periodic table not being identified for another 50 years, Mendeleev was able to predict correctly a number of elements that had yet to be identified but which were expected to exist if the repeating periodic structure of the table was correct. These elements included gallium and germanium, whose properties Mendeleev had been able to outline because of their membership in groups of poor metals that included known elements such as aluminum and silicon, respectively (hence Mendeleev's original names of "eka-aluminum" for gallium and "eka-silicon" for germanium). One of the great strengths of a theoretically based classification system, therefore, is that it can predict the existence of yet-to-be identified members of the system or can lead to a reclassification of members that have been misclassified under previous systems."