Assertion :First period of periodic table is the shortest period. Reason: K shell can accommodate a maximum of two electrons.

Both Assertion and Reason are correct and Reason is the correct explanation for Assertion.

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Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion.

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Assertion is correct but Reason is incorrect.

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Assertion is incorrect, but reason is correct.

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Solution

The correct option is A Both Assertion and Reason are correct and Reason is the correct explanation for Assertion.
The elements of first period have only K shell.
K shell can accommodate only $2$ electrons.
Thus first period has only $2$ elements.
Hence first period is the shortest one.
Thus assertion and reason are true with reason explaining assertion.

Hence, option (A) is the correct answer.

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Similar questions

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Assertion (A) Order of the reaction can be zero or fractional.

Reason (R) We cannot determine order from balanced chemical equation.

(a) Both assertion and reason are correct and the reason is correct explanation of assertion
(b) Both assertion and reason are correct, but reason does not explain assertion.
(c) Assertion is correct, but reason is incorrect
(d) Both assertion and reason are incorrect
(e) Assertion is incorrect but reason is correct.

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Reason (R) Order is determined experimentally and molecularity is the sum of the stoichimetric coeffcient of rate determining elementary step.

ASSERTION: n-Pentane and n-Hexane belong to a homologous series.

REASON: n-Pentane and n-Hexane belong to the same class of hydrocarbons and they differ by a - $C H_{2}$ - group.

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