State the merits of Mendeleev's periodic table.

Explanation

Merits of Mendeleev's periodic table:
i. Mendeleev was the first to successfully classify all known elements.
ii. Mendeleev's periodic table helped to revise the atomic masses of some elements so as to give them proper places in the periodic table in accordance with their properties. For example, the atomic mass of beryllium (Be) was previously determined to be 14.09. This value was changed to the correct value of 9.4 and beryllium (Be) was placed before boron (B).
iii. Mendeleev's periodic table had left some vacant spaces in it. These were for elements that were yet to be discovered. Three of these unknown elements were named eka-boron, eka-aluminium and eka-silicon . He predicted properties of these elements even before they were discovered. These elements are scandium (Sc), gallium (Ga) and germanium (Ge) respectively . The properties of these elements matched well with those predicted by Mendeleev.
iv. There was no place reserved for noble gases in Mendeleev's original periodic table . But, when noble gases were discovered later, they were placed in a new group called as 'zero group' in Mendeleev's periodic table without disturbing the positions of other elements.