Question

Which of the following is true regarding the reactivity order of alkali metals towards hydrogen?

(a) Li < Na < K > Rb

(b) Lithium < Na < K < Rb < Cs

(c) Li > Na < Cs

(d) Li < Rb > Cs

I got this question during an online interview.

My doubt stems from s-Block Elements in section s-Block Elements of Chemistry – Class 11

Answer 1

The correct option is (b) Lithium < Na < K < Rb < Cs

To explain I would say: Two moles of alkali metal reacts with one mole of hydrogen molecule in order to form 2 moles of alkali metal hydride. The correct order of reactivity of alkali metals towards hydrogen is Li < Na < K < Rb < Cs.