Which element has the lowest density of all metals?

Lithium has the lowest density of all metals.

Lithium is an alkali metal with the chemical symbol Li and atomic number 3. Its density is about 0.534 grams per cubic centimetre, making it less dense than water. A piece of lithium can float briefly, although it reacts with water and should never be handled casually.

Lithium is soft, silvery, and highly reactive. It is widely used in rechargeable batteries, where lithium ions move between electrodes during charging and discharging. It is also used in some ceramics, glass products, lubricating greases, and pharmaceutical compounds.

Sodium and potassium are also less dense than water, which sometimes causes confusion. Lithium is the lightest solid element and the least dense metal, while hydrogen is the least dense element overall but is not a metal under ordinary conditions.