Over 100 Short Q&A for Periodic Classification of Elements (Class 11 NCERT) Part 1: Genesis of Classification & Modern Periodic Table Q. No. Question Answer 1 Who first classified elements into triads? Johann Dobereiner. 2 State Dobereiner's Law of Triads. The atomic mass of the middle element is approximately the arithmetic mean of the other two. 3 Who proposed the Law of Octaves? John Newlands. 4 What was the basis of Newlands' classification? Increasing atomic masses (properties repeated every eighth element). 5 What was the major criterion for Mendeleev's classification? Atomic weight (mass) and similarity in chemical properties (oxide and hydride formulas). 6 State Mendeleev's Periodic Law. The properties of elements are a periodic function of their atomic weights. 7 Name an element whose existence was predicted by Mendeleev as 'Eka-silicon'. Germanium (Ge). 8 What was the main drawback of Mendeleev's Periodic Table regarding position? The pos...