Choose the correct order of density of the alkali metals

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:

$Li < K < Na < Rb < Cs$