Question

Assertion :

According to Mendeleev's periodic law:

The properties of elements is the periodic function of their atomic numbers.

Reason :

Mendeleev's periodic law could not explain the phenomena of anomalous pairs.

• A. Both assertion and reason are correct and reason is the correct explanation of the assertion.
• B. Both assertion and reason are correct, but reason is not the correct explanation of the assertion.
• C. Assertion is correct, but reason is incorrect.
• D. Assertion is incorrect, but reason is correct.
• E. Both assertion and reason are incorrect.

Answer 1

The correct option is D Assertion is incorrect, but reason is correct.

According to Mendeleev's periodic table, it was atomic weight on which all the properties depends upon.

It failed because of anomalous pairs, where the atomic weight of the first atom which is more is being arranged in the periodic table before that of the atom that has a smaller atomic weight.

These are called anomalous pairs.

Mendeleev's told that atomic weight keeps on increasing as we move in a periodic table but it violated the rule.

Hence, Assertion is incorrect, but reason is correct.

Hence option D is the correct answer.