Periodicity among elements in Newlands Octaves was observed up to _________ only.

Correct option is A

​The correct answer is (a) Ca ( Calcium ) .

Information booster :

• Periodicity among elements in Newlands' Law of Octaves was observed up to calcium (Ca) only.
• This limitation arose because Newlands arranged elements based on increasing atomic weights and, beyond calcium, the properties of the elements did not fit into the octave pattern , 
• The Law of Octaves was proposed by John Newlands in 1864 as an early attempt to organize chemical elements based on their properties.
• Newlands arranged the known elements in increasing order of their atomic weights.
• He noticed that every eighth element had properties similar to the first, much like the octaves in music. Hence, he called this relationship the "Law of Octaves."
• In this arrangement, Lithium (Li) and Sodium (Na) are in the same group because they exhibit similar properties, and the same pattern applies to other pairs like Fluorine (F) and Chlorine (Cl).​
  

1. The law worked only for the first 17 elements (up to Calcium). Beyond Calcium, elements did not follow the periodic pattern.
2. It did not account for the discovery of noble gases, which were unknown at the time.
3. Strict adherence to increasing atomic weight led to the grouping of some elements with dissimilar properties.