Dobereiner's Triads:
- Advantage: Successfully grouped elements with similar properties into triads, showing a pattern in atomic weights and properties.
- Limitation: Applicable only to a limited number of elements; many elements did not fit into triads.
Newland's Law of Octaves:
- Advantage: Suggested a periodic relationship between elements, with properties repeating every eighth element (similar to musical octaves).
- Limitation: Worked well only for lighter elements; the pattern broke down for heavier elements. It also forced dissimilar elements into the same group.
Mendeleev's Periodic Table:
- Advantage: Arranged elements based on increasing atomic weights and recurring chemical properties, leaving gaps for undiscovered elements which were later found and their properties matched his predictions.
- Limitation: Some elements were placed out of order of atomic weight to maintain the correct chemical family grouping; this was later explained by the concept of isotopes and a better understanding of atomic structure (atomic number).