Consider the below statements and identify the correct answer.
Statement I: Dobereiner gave the law of triads.
Statement II: Dobereiner tried to arrange the elements with different properties into groups, having three elements each.

Correct option is D

(d) Only Statement I is correct.

Explanation:

• Statement I: Dobereiner gave the law of triads is correct. Johann Wolfgang Dobereiner proposed the Law of Triads in the early 19th century, which was a method of grouping elements with similar chemical properties into sets of three, known as "triads." He observed that the atomic mass of the middle element in a triad was approximately the average of the atomic masses of the other two elements.

• Statement II: Dobereiner tried to arrange the elements with different properties into groups, having three elements each is incorrect. Dobereiner’s triads were based on the grouping of elements with similar properties, not elements with different properties. The purpose was to observe a pattern of similarities in properties, particularly in the case of elements that belonged to the same chemical group.

Therefore, Statement I is correct, but Statement II is not an accurate explanation of Statement I.

Important Key Points:

1. Law of Triads: Dobereiner classified elements into groups of three, where the middle element's atomic mass was approximately the average of the other two elements.
2. Dobereiner's law was one of the earliest attempts to categorize elements based on their properties, which laid the foundation for the modern Periodic Table.
3. The Law of Triads applied to elements such as lithium, sodium, and potassium (alkali metals) and chlorine, bromine, and iodine (halogens).
4. Later, Mendeleev's Periodic Table refined the idea of periodicity and classification, which Dobereiner had started with the triads.
5. The triad system was not as comprehensive as the Periodic Table that came later, but it showed the early recognition of periodic relationships between elements.

Knowledge Booster:

• Mendeleev’s Periodic Table was based on atomic mass and was able to arrange more elements systematically, correcting errors in Dobereiner’s triads.
• Triads were an early way to understand the relationship between elements, and although the law did not hold universally, it was a significant early step in the development of the periodic classification of elements.