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
Dense order a set "X" to be dense are: None of them are necessary. A non-empty and dense relation cannot be antitransitive. A strict partial order < is a dense order iff < is a dense relation. A dense relation that is also transitive is said to be idempotent. Dense order In mathematics, a partial order or total order < on a set "X" is said to be dense if, for all "x" and "y" in "X" for which "x" < "y", there is a "z" in "X" such that "x" < "z" < "y". The rational numbers with the ordinary ordering