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MCQEasyJEE 2025Modern Periodic Table

JEE Chemistry 2025 Question with Solution

Given below are two statements: Statement (I): According to the Law of Octaves, the elements were arranged in the increasing order of their atomic number. Statement (II): Meyer observed a periodically repeated pattern upon plotting physical properties of certain elements against their respective atomic numbers. In the light of the above statements, choose the correct answer from the options given below:

  • A

    Both Statement I and Statement II are false

  • B

    Statement I is true but Statement II is false

  • C

    Both Statement I and Statement II are true

  • D

    Statement I is false but Statement II is true

Answer

Correct answer:D

Step-by-step solution

Standard Method

Given: Two historical statements about the development of periodic classification are to be checked.

Find: Which option correctly identifies the truth values of Statement (I) and Statement (II).

For Statement (I), the Law of Octaves was proposed by John Newlands. In this classification, elements were arranged in the increasing order of atomic mass, not atomic number. Therefore, Statement (I) is false.

For Statement (II), Lothar Meyer studied periodicity by plotting physical properties such as atomic volume and observed a repeating pattern. The solution states this periodic pattern is considered true in the context of the development of periodic law. Therefore, Statement (II) is true.

So, Statement (I) is false but Statement (II) is true.

Therefore, the correct option is D.

Common mistakes

  • Confusing atomic mass with atomic number in early periodic classifications. Newlands and Meyer worked with atomic masses, so assigning atomic number directly to the Law of Octaves makes Statement (I) incorrect.

  • Rejecting Statement (II) only because Meyer originally used atomic mass. The key point is that he observed a periodically repeated pattern in physical properties, so the statement is treated as true in this question's context.

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