Question

State Newlands law of octaves. Give one of its limitation.

Answer 1

Newlands law of octaves state that, when elements are arranged in increasing order of their atomic masses then the properties of every eighth element is similar to its first.

In 1865, an English chemist John Newlands stated a theory known as the Newland's law of octaves. At that time only 56 elements were known. He arranged all the elements in increasing order of their atomic masses (Hydrogen having the lowest atomic mass was placed first and the last element was thorium which had the highest atomic mass at that time). He observed that every eighth element had the same properties as that of the first element.

Limitation of this law:

In order to prove his law, Newlands placed two elements in the same slot. Also, elements having different properties lied under the same note. And at some places elements having same properties were placed away from each other.

For example, $Co$ and $Ni$ were placed in the same slot and were in the same column as $F,Cl$ and $Br$. Similarly, $Fe$ was not placed in the column containing $Co$ and $Ni$, though they have similar properties.