Assertion: Alkali metals have a low ionization energy.
Reason: Alkali metals have only one valence electron that is easily removed, resulting in a low ionization energy.
Both Assertion (A) and Reason (R) are the true and Reason (R) is a correct explanation of Assertion (A).
Both Assertion (A) and Reason (R) are the true but Reason (R) is not a correct explanation of Assertion (A).
Assertion (A) is true and Reason (R) is false.
Assertion (A) is false and Reason (R) is true.
The assertion is true because alkali metals have only one valence electron, which is loosely held and easily removed. This results in a low ionization energy, which is the energy required to remove an electron from an atom or ion in the gaseous state. Because of the low ionization energy, alkali metals readily form cations (positively charged ions) by losing their single valence electron. This characteristic of alkali metals also makes them highly reactive, as they readily combine with other elements to form compounds.