Q6 of 60 Page 140

When Mendeleev started his work, the number of known elements was:

When Mendeleev started the work, many elements were not even discovered. Example – noble gases.

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4

The element with atomic number 18 belongs to which group:

 5

The scientist who showed that the atomic number of an element is a more fundamental property than its atomic mass is:

 7

It was assumed by Newlands that only:

 8

Doberiener’s system of classification into triads was not found to be useful as he could identify only: