According to Newlands’ Law of Octaves, the properties of lithium and sodium were found to be similar.
According to Newland’s Law of Octaves, the then known elements when arranged in the increasing order of their atomic masses, it is found that every eighth element had properties similar to that of the first. In Newlands' Octaves, the properties of lithium and sodium were found to be same. Sodium is the eighth element after lithium. Similarly, beryllium and magnesium resemble each other. Same is the case with boron and aluminium.
The arrangement of few elements is as follows: (Noble gases were not discovered at that time.)