Why do lithium, sodium and potassium float on water?

1 Answer

They all have densities that are less than water's.


Lithium, sodium, and potassium are all very light elements, and metals that are made purely of them will have low densities.

In fact, lithium has the lowest density of all solid elements, #"0.534 g/cm"^3# compared to water with #"1.000 g/cm"^3#. They also all react violently with water, so even though they float, they won't stay there for very long.