Question

Why Sodium and potassium inspite of being metals float on the water?

Answer 1

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.