CBSE Class 10 Science 2022 · Paper 31(B)/6 · Question 2(b)

Newlands' law of octaves: when the elements are arranged in the order of increasing atomic masses, every eighth element has properties similar to those of the first, like the eighth note of a musical scale. For example, counting lithium as the first, the eighth element is sodium, and the two have similar properties. Two drawbacks (any two of these): 1. The law held only up to calcium. After calcium, every eighth element did not have properties similar to the first, so it worked well only for the lighter elements. 2. To fit the elements into his table, Newlands put two elements into one slot and placed unlike elements under the same note: cobalt and nickel share a slot under the same note as fluorine, chlorine and bromine, although their properties are quite different, while iron, which resembles cobalt and nickel, was placed far from them. 3. Newlands assumed that only 56 elements existed and that no more would be discovered; elements discovered later did not fit into the law.