Lithium is a chemical element with the symbol Li and atomic number 3. It’s a soft, silvery-white alkali metal. Lithium is highly reactive and flammable, and can quickly corrode in humid air, so it’s not found in its elemental form in nature. Instead, it’s usually found in minerals and salts. Lithium has a variety of applications, including being used in batteries, ceramics, glasses, lubricants, and even medicine. It has become a vital component in rechargeable batteries used in smartphones, laptops, and electric vehicles, where it has replaced traditional heavy metals. In addition, lithium is used to treat mood disorders such as bipolar disorder, depression, and mania.