Lithium be cut with a knife. When cut, it possesses a silvery-white color that quickly changes to gray as it oxidizes to lithium oxide. While it has one of the lowest melting points among all metals (180 °C), it has the highest melting and boiling points of the alkali metals. Lithium has a very low density (0.534 g/cm), comparable with pine wood. It is the least dense of all elements that are solids at room temperature; the next lightest solid element (potassium, at 0.862 g/cm) is more than 60% denser. Furthermore, apart from helium and hydrogen, it is less dense than
Greatest and least elements Greatest and least elements In mathematics, especially in order theory, the greatest element of a subset "S" of a partially ordered set (poset) is an element of "S" that is greater than every other element of "S". The term least element is defined dually, that is, it is an element of "S" that is smaller than every other element of "S". Formally, given a partially ordered set ("P", ≤), an element "g" of a subset "S" of "P" is the greatest element of "S" if Hence, the greatest element of "S" is an upper bound of "S" that is contained