Alkali metals react with water vigorously to form hydroxides and dihydrogen. Which of the following alkali metals reacts with water least vigorously?

The correct option is A Li

Reaction of alkali metals with water

Alkali metals react with water to form hydroxides and dihydrogen.

$2M+2H_{2}O\to 2M^{+}+2O{H}^{-}+H_2$ where $M$ is an alkali metal.

It may be noted that although lithium has

most negative $E^0$ (reduction potential)

value, its reaction with water is less vigorous than that of other alkali metals which has the least negative $E^0$ (reduction potential) value. This behaviour of lithium is attributed to its small size and very high hydration energy. Due to this, other metals of the group react explosively with water.

So, the correct answer is an option $\left(A\right).$