Dobereiner’s Triads
Dobereiner arranged a group of three elements with similar properties in the order of increasing atomic masses and called it a triad. He showed that the atomic mass of the middle element is approximately the arithmetic mean of the other two. But, Dobereiner could identify only the following three triads from the elements known at that time.
Newlands’ Law of Octaves
| sa (do) | re (re) | ga (mi) | ma (fa) | pa (so) | da (la) | ni (ti) |
| H | Li | Be | B | C | N | O |
| F | Na | Mg | Al | Si | P | F |
| Cl | K | Ca | Cr | Ti | Mn | Fe |
| Co and Ni | Cu | Zn | Y | In | As | Se |
| Br | Rb | Sr | Ce and La | Zr | ______ | _____ |
When the elements are arranged according to increasing atomic masses, the physical and chemical properties of every eighth element are similar to that of the first.
Newlands compared these octaves to the series of eight notes of a musical scale.
Assumptions and Limitations:
1. The law was applicable for elements with atomic masses up to 40.
2. Properties of new elements discovered did not fit into the law of octaves.
3. In a few cases, Newlands placed two elements in the same slot to fit elements in the table.
4. He also grouped unlike elements under the same slot.