Formation of Oxides in Air

• Highly electropositive, the group one metals react with the oxygen in air. For this reason, cesium has been used as an "oxygen getter" in electron tubes, ferreting out traces of oxygen to protect the heated filament. If there is moisture present, the alkali oxide becomes the corresponding alkali hydroxide. Over time, alkali oxides or hydroxides exposed to it absorb carbon dioxide gas to form the alkali carbonate. When heated, this reaction is reversible and carbon dioxide gas is driven back out, leaving the oxide. The reactivity increases the further down the periodic table the alkali metal is located.
  
  

Peroxides and Superoxides

• Hydrogen forms a peroxide. Dilute hydrogen peroxide is used for disinfectant purposes and as a bleaching agent. Higher concentrations of hydrogen peroxide, such as 30 percent or more are aggressive and may produce burns. At the high end, hydrogen peroxide may be used as an oxidizer for rocket fuel. Group one metals can react with oxygen to an even greater extent, producing not only peroxides but also superoxides and even ozonides. Sodium peroxide is used to bleach wood pulp for paper. It is also used in the manufacture of textiles. Lithium peroxide is especially useful for removing carbon dioxide from space vehicles.
  
  

Reaction with Liquid Water

• Lithium reacts strongly with water but not violently. Sodium reacts more strongly with water, evolving hydrogen gas that catches fire and burns with an orange flame. Potassium reacts still more strongly, immediately producing a lilac flame. Rubidium and cesium are violently reactive. Cesium sometimes shatters a glass container -- the result of shock wave generation due to the speed of hydrogen gas evolution.
  
  

Acid-Base Reactions

• The reaction with mineral acids and alkali metals is a classic schoolroom demonstration. The most famous is the reaction between sodium metal and hydrochloric acid to produce sodium chloride and hydrogen gas. If sodium hydroxide is used in place of the metal, the products are sodium chloride and water. If the carbonate is used, the products are sodium chloride and carbonic acid. This last reaction demonstrates how the salt of a strong base with a weak acid (sodium hydroxide, a strong base and carbonic acid, a weak acid) reacts with a stronger acid to produce the salt of a strong acid and strong base and liberates the weak acid.
  
  

Forming Organometallic Reagents

• Alkali metals form very reactive substances with certain organic compounds. Dissolved in solvents such as tetrahydrofuran or ether, they can be used in the laboratory for important synthesis reactions. These reactions are somewhat analogous to the magnesium organometallic compounds in solvents called Grignard reagents.