Assertion :Group I ( $1 s$ ) elements are known as the alkali elements. Reason: $S -$ orbital can accommodate only two electrons.

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

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Both Assertion and Reason are correct, but Reason is not the correct explanation of 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 B Both Assertion and Reason are correct, but Reason is not the correct explanation of assertion.
Assertion:
Group I $(1 s)$ elements are known as the alkali elements as they form oxides and hydroxides which combine with water to form alkali. Alkali word is derived from the Arabic word 'alquis' which means plant ashes which are rich in sodium carbonate and potassium carbonate.

Reason:
According to Pauli’s exclusion principle, an ss orbital contains at most two electrons with the opposite spin (up and down).

$s -$ orbital can accommodate only two electrons. A $p$ orbital can accommodate six electrons and d orbital can accommodate 10 electrons.

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

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Choose the correct option.

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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Assertion :Group I (1s) elements are known as the alkali elements. Reason: S−orbital can accommodate only two electrons.

Assertion :Group I ( $1 s$ ) elements are known as the alkali elements. Reason: $S -$ orbital can accommodate only two electrons.