Choose the correct order of density of the alkali metals: (A) Li < K < Na < Rb < Cs (B) Li < Na < K — s Block Elements Chemistry Question

💡 Solution & Explanation

On going down the group, both the atomic size and atomic mass increase but the increase in atomic mass compensates the bigger atomic size. As a result, the density of alkali metals increases from Li to Cs. Potassium is, however, lighter than sodium. It is probably due to an unusual increase in atomic size of potassium. Hence, the correct order of density of alkali metals is: Li < K < Na < Rb < Cs