Lithium in paraffin (Public Domain, source: Wikipedia)
Lithium is nature’s lightest metal, with an atomic number of 3. It’s a good conductor of heat and electricity and is about as dense as pine wood. You can cut it with a knife, it’s that soft. Because it reacts so readily with water, it’s usually stored in oil, petroleum jelly, or paraffin.
In medicine, it’s helpful in the treatment of bipolar disorder. It’s an alkaline metal, so you probably see it most frequently in rechargeable batteries, especially laptop batteries. Lithium-ion batteries are more expensive than nickel-metal-hydride ones, but are lighter and less bulky, and recharge quicker and are less prone to the “memory effect” than their nickel counterparts, at the cost of expected life (i.e. they last shorter than NiMH batteries). Some jurisdictions put restrictions on the number of lithium batteries you can purchase, because lithium can be used in one of the methods used to create methamphetamine.
Can you think of other uses for lithium?