The Group 1 elements other than hydrogen are called the alkali metals. The Group 1 elements are:
The Group 1 metals are all highly reactive metals that are so reactive that they are generally found in nature combined with other elements. They are all soft and can be cut easily with a knife.
Hydrogen is usually placed at the top of the Group but is not a Group 1 metal. The electronic configuration of the metallic elements consists of a lone s-electron outside an inner core of electron corresponding to the previous inert gas. The metals all react with water with increasing severity down the Group. In each case the result is the evolution of hydrogen and formation of alkaline solutions:
M + 2H2O → 2MOH(aq) + ↑H2
The alkali metals react readily with atmospheric oxygen and water vapor. (Lithium also reacts with nitrogen.) They react vigorously, and often violently, with water to release hydrogen and form strong caustic solutions. Most common nonmetallic substances such as halogens, halogen acids, sulfur, and phosphorus react with the alkali metals. The alkali metals themselves react with many organic compounds, particularly those containing a halogen or a readily replaceable hydrogen atom.
Sodium is by far the most important alkali metal in terms of industrial use. The metal is employed in the reduction of organic compounds and in the preparation of many commercial compounds. As a free metal, it is used as a heat-transfer fluid in some nuclear reactors. Hundreds of thousands of tons of commercial compounds that contain sodium are used annually, including common salt (NaCl), baking soda (NaHCO3), sodium carbonate (Na2CO3), and caustic soda (NaOH). Potassium has considerably less use than sodium as a free metal. Potassium salts, however, are consumed in considerable tonnages in the manufacture of fertilizers. Lithium metal is used in certain light-metal alloys and as a reactant in organic syntheses. An important use of lithium is in the construction of lightweight batteries. Primary lithium batteries (not rechargeable) are widely used in many devices such as cameras, cellular telephones, and pacemakers. Rechargeable lithium storage batteries that could be suitable for vehicle propulsion or energy storage are the subject of intensive research. Rubidium and cesium and their compounds have limited use, but cesium metal vapor is used in atomic clocks, which are so accurate that they are used as time standards.