Write any three merits of Mendeleev’s periodic table.

Answer:

1. Gaps for undiscovered elements: Mendeleev left vacant places in his table and predicted the properties of the elements that would fill them, naming them eka-boron, eka-aluminium and eka-silicon. Scandium, gallium and germanium, discovered later, matched his predictions closely.
2. Correction of atomic masses: Where the properties of an element did not fit its place, he doubted and revised its atomic mass. For example, the atomic mass of beryllium was corrected from 14.09 to 9.4.
3. Place for noble gases: When the noble gases (helium, neon, argon, etc.) were discovered later, they were placed in a separate ‘zero’ group without disturbing the original arrangement.

Also, elements with similar properties were brought together in the same group, which made their systematic study easier.