JEE Main202225 Jul 2022Morning ShiftChemistrys Block ElementsActual
Choose the correct order of density of the alkali metals
Options
- ALi <   K < Na < Rb < Cs
- BLi <   Na < K   < Rb < Cs
- CLi < Na < K < Cs < Rb
- DCs < Rb < K < Na < Li
Correct answer
A. Li <   K < Na < Rb < Cs
Step-by-step solution
As we move down the group from Li to Cs , both the atomic size and atomic mass increase. But the increase in atomic mass more than compensates the bigger atomic size. As a result, the densities of alkali metals increase from Li to Cs . Potassium is, however, lighter than sodium. Hence, the increasing order of density is as given below: Li <   K < Na < Rb < Cs