Lithium Lithium Lithium (from ) is a chemical element with symbol Li and atomic number 3. It is a soft, silvery-white alkali metal. Under standard conditions, it is the lightest metal and the lightest solid element. Like all alkali metals, lithium is highly reactive and flammable, and is stored in mineral oil. When cut, it exhibits a metallic luster, but moist air corrodes it quickly to a dull silvery gray, then black tarnish. It never occurs freely in nature, but only in (usually ionic) compounds, such as pegmatitic minerals which were once the main source of lithium. Due to its solubility
Isotopes of niobium Isotopes of niobium Naturally occurring niobium (Nb), is composed of one stable isotope (Nb). Nb is the lightest nuclide theoretically susceptible to spontaneous fission, and although this has never been observed, it makes niobium theoretically the lightest element with no stable isotope. The first 40 elements (to zirconium) all have at least one stable nuclide susceptible in theory only to proton decay. The most stable radioisotope is Nb with a half-life of 34.7 million years. The next longest-lived niobium nuclides are Nb (half-life: 20,300 years), and Nb with a half-life of 680 years. There is also a meta state at