Dobereiner arranged three element that the average of the two elements atomic weight give the middle elements atomic weight
Newland
An English chemist Alexander Newland
Newland's law of octave
He arranged the 56 elements known then in increasing order of their atomic weight. He observed the property of every eighth element is similar to the first one.
The limitation of Newland's classification
1.The inert gases were not discovered till then
2.Beyond Ca, this repetition was not observed.
Mendleev
A Russian chemist
Mendleev's classification
He arranged the elements in order of increasing atomic weights and observed that elements with similar properties (in families) appeared at regular intervals
Mendeleev’s Periodic Law
1.consisted of only 63 elements, inert gasses were not yet discovered.
2.These elements were arranged in seven horizontal rows called as periods and eight vertical columns called as groups.
3.He left some vacant for undiscovered elements by predicting their property
