Aluminum is the most plentiful metal in the Earth's crust. Of the elements in Group 13 (of the Periodic Table), aluminum has the most practical uses. With three electrons in its outer level(valence shell), aluminum is less metallic than the other elements of Groups 1 and 2. In forming compounds, it tends to share electrons rather than form ions. It is also less reactive than the elements of groups 1 and 2 metals. One aluminum compound, aluminum sulfate, is used in water purification, paper manufacture, and fabric dyeing. Large amounts of elemental aluminum are used to produce lightweight alloys for many items from soft drink cans to spacecraft.