Lithium

Because it combines three unique advantages: it is the lightest metal, it cedes its electron easily, and its tiny ions move quickly between electrodes. This gives batteries with high energy per kilogram and thousands of charge cycles. No other element combines so much lightness and electrochemical potential at once, although sodium is starting to compete in cheap stationary applications.

Yes. Lithium salts, especially carbonate, stabilize mood in bipolar disorder and reduce the risk of relapses and suicide for more than half a century. But the margin between effective and toxic dose is narrow, so treatment requires periodic blood tests, kidney function control and constant medical supervision. Nothing to do with battery lithium: no one should self-medicate.

Yes, and it is increasingly profitable: spent batteries are crushed and lithium is recovered by hydrometallurgical processes together with cobalt, nickel and copper. Today only a small fraction is recycled because most batteries are still in use, collection fails and many end up stored in drawers. With millions of electric cars retiring in the next decade, recycling will be a true essential "urban mine".

Because it is the least dense metal that exists (0.534 g/cm³): it floats even in mineral oil where it is stored. On contact with water it reacts releasing hydrogen, but with less violence than sodium or potassium, without melting or burning. It moves across the surface effervescing and bubbling until it dissolves completely as lithium hydroxide, a reaction that is spectacular but controllable.

It is the Andean region where Argentina, Bolivia and Chile converge, whose salt flats concentrate more than half of the world's lithium resources in brine. Salty groundwater is pumped to large solar evaporation ponds, where sun and wind concentrate it for months until salts precipitate. Its exploitation generates debate over water consumption in one of the planet's most arid deserts.

It is the least reactive alkali metal: it attacks water without inflaming and only forms the normal oxide, never peroxides or superoxides like its siblings. Its tiny ion, with high charge density, polarizes anions and gives it a covalent air that recalls magnesium (diagonal relationship). In addition, it is the only one of the group that forms nitride directly with nitrogen (Li₃N). In return, it is more expensive and scarcer than sodium or potassium.

Not in the short term: identified resources exceed 100 million tonnes and grow each year with new prospecting in salt flats, pegmatites and clays. The bottleneck is the pace of mine and refinery opening, concentrated in few countries. In the long term, massive battery recycling and emerging alternatives such as sodium batteries will alleviate pressure on this strategic metal.