Newland’s Law of Octaves: Advantages, Limitations and Sample Questions

Ans. The law of octaves stated that if chemical elements were organized by increasing the atomic weight, those with similar physical and chemical properties appear after each interval of seven elements.

When the elements are organized in increasing order of their atomic masses, the law of octaves asserts that "Every eighth element has similar properties as the eighth element."

Newlands contrasted the components' closeness to musical octaves, in which every eighth note is equivalent to the first. This was the first time an atomic number was assigned to each element. Throughout the arrangement, the Newland Law of Octaves was not applied. It was only valid till calcium was reached. Only lighter elements with atomic weights up to 40 u, i.e., up to calcium, were covered by Newland's law of octaves. After calcium, no eighth element had qualities that were similar to those of the first.

As a result, Newland's law of octaves for element classification was discovered to be valid only up to calcium. As a result, option B is the required response.

Note: Newlands predicted that only 56 elements would exist in nature and that no new elements would be discovered. Mendeleev, on the other hand, purposefully included gaps in his periodic table so that newly discovered elements might be included.

Ans. The following were the primary drawbacks:

1. It only applied to elements with atomic weights of up to 40 u, or up to calcium. After calcium, the first and eighth elements did not have the same properties.
2. There were only 63 elements thought to exist in nature, and no new elements were expected to be discovered in the future. However, the table later encountered several new components whose properties did not fit the law of octaves.
3. Some similar parts have been separated from one another, while others that are not similar have been grouped in the same column.
4. When noble gases were found, the properties of the eighth element were no longer identical to those of the first. It was now the first and ninth which has the same properties as another element

Ans. Johann Wolfgang Dobereiner, a German scientist, discovered Dobereiner's triads, which were groups of elements having similar properties. Dobereiner discovered that a set of three elements (known as triads) could be identified, all of which possessed similar physical and chemical properties. In the year 1817, Dobereiner developed the first of his triads. Calcium, strontium, and barium, alkaline earth metals, started it.

Ans. (a) Dobereiner:

• Advantage: Group three elements have similar kinds of properties and are known as Dobereiner triads. He organized them in an increasing atomic mass format and the mass of the element in the center was the same as the average of the other two elements.
• Limitation: He was successful in pointing out four triads but could not succeed in his effort to group nitrogen, phosphorus and arsenic because phosphorus's atomic mass is not the same as the average of the two.

Newland:

• Advantage: Newland’s law establishes a framework for classifying items with similar features into groups.
• Limitation: Newland’s law was appropriate in arranging lighter elements.

Mendeleev:

• Advantage: He organized the elements in ascending order according to their atomic mass and also rectified the mass of beryllium changing it from 4.5 to 13.5 u.
• Limitation: The placement of hydrogen and the isotopes were unjustified in his periodic table.

(b) Henry Moseley was the scientist who first of all showed that the atomic number of an element is a more fundamental property than its atomic mass.

(c) According to the law of the modern periodic table, the characteristics of the elements can be referred to as the periodic function of their atomic figure. The repetition of such characteristics take place due to the similarity of the external electronic configuration.