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 set space "X" is the least cardinality of a dense subset of "X". An alternative definition of dense set in the case of metric spaces is the following. When the topology of "X" is given by a metric, the closure formula_1 of "A" in "X" is the union of "A" and the set of all limits of sequences of elements in "A" (its "limit points"), Then "A" is dense in "X" if Note that formula_4. If formula_5 is a sequence of dense open sets in a complete metric space, "X", then formula_6 is also dense in "X". This fact is one