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

M + 2H2O  → MOH + 1/2 H2↑Reactivity with H2O Reactivity with water increases,As the size of alkali metal increasesReason: As the size of alkali metal increases             Electron losing tendency increases and hence reactivity increases→ Therefore "Li" is the least reactive with water