State the merits of Mendeleev's classification of elements.
The merits of Mendeleev's classification of elements:
1. Mendeleev's periodic law predicted the existence of certain elements such as gallium, scandium and germanium, which were not discovered at that time.
2. Mendeleev's periodic table could also predict the properties of various elements based on their position in the periodic table.
3. Mendeleev's periodic table could place group 18 elements, called Noble gases in the periodic table, when they were discovered.