Assertion: Alkali metals have low melting and boiling points.
Reason: Alkali metals have weak metallic bonds due to the presence of a single valence electron in their outermost shell.
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 relatively weak metallic bonds compared to other metals. This is because they have only one valence electron, which is loosely held and easily removed, resulting in the formation of positively charged ions that are attracted to each other due to electrostatic forces. These forces are relatively weak, so the metals have low melting and boiling points.