Newlands’ Law of Octaves
- This classification was done by John Newlands in 1866.
- John Newlands arranged the elements in increasing order of atomic masses
- He started with element having lowest atomic mass and made group of 8 elements (called octaves)
- He started with lowest atomic mass (Hydrogen) and ended with (Thorium)
- He observed that every 8th element has properties similar to the first element.
- He could observe this pattern in a total of 56 elements in nature.
This concept was based on musical notes like
Sa Re Ga Ma Pa Dha Ni Sa
( Note - Eighth word is similar to the first word)
Similarly,in English system of music
Do Re Mi Fa So La Ti Do
( Note - Eighth word is similar to the first word)
Here we can see that:
- Sodium (Na) is the eighth element after Lithium (Li) and Potassium (K) is eighth after Sodium; their properties were found to be similar as well.
- Similarly, Calcium (Ca) is the eighth after Magnesium and Magnesium (Mg) is the eighth element after Beryllium (Be) and they have similar properties.
Note: Li, Na, K is also a Döbereiner’s triad.
Limitations of Newland Law of Octaves
-
Law of Octaves is applicable only till Calcium
After that properties of 8th element does not match with those of the first element
-
The assumption that only 56 elements existed in nature was wrong
Newland wrongly assumed that there were only 56 elements in nature. Later many more elements were discovered which could not be placed appropriately in the law of octaves.
- Unlike element have been put in same column and similar elements were placed in different columns
- Cobalt and Nickel were placed together in one slot in order to fit elements. He also placed them in the same column with Fluorine, Chlorine and Bromine though they have very different properties.
- Also, Iron has properties similar to Cobalt and Nickel. But it has been placed far away from these elements.
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Did not include Noble Gas
When Noble gases were discovered, the Law of Octaves become irrelevant
(as Noble gas did not fit into this law )
[The Noble gases are Helium (He), Neon (Ne), Argon (Ar), Krypton (Kr), Xenon (Xe) and Radon (Rn)]
