Notes On Alkali Metals: General Characteristics And Properties - CBSE Class 11 Chemistry
 Group 1 metals are also called as alkali metals. These are the most reactive metals. They contain only one electron in its valence shell thus they form +1cations. The alkali metals are good conductors, and they have a shiny, silvery appearance. In flame tests, lithium forms a candy-apple red colour, while sodium produces a yellow flame and potassium a lilac flame. Chemical properties: They react with hydrogen to form metal hydrides. 2M + H2 → 2MH (Where M= Li, Na, K, Rb, Cs) They react with halogens to form alkali metal halide salts, such as NaCl. 2Na + Cl2 → 2NaCl They react with oxygen lithium forms oxides, sodium forms peroxides, and the other group 1 metals form superoxides. 4Li + O2 → 2Li2O (Lithium oxide) 2Na + O2 → Na2O2 (Sodium peroxide) M + O2 → MO2 Where M = K, Rb, Cs   Alkali metals react vigorously with water to produce hydroxide ions in solution, and hydrogen gas.  Applications: An alloy with lead is used to make engine parts, an aluminium-lithium alloy is used in airplane construction and a magnesium-lithium alloy is used to make armour plates. Lithium metal is used in some thermonuclear reactions and to construct various types of batteries. Sodium-lead alloy was used to produce organo-lead compounds such as tetraethyl lead, which was used as an anti-knock agent in automobile fuel.  Potassium has a variety of roles in biological systems.  Potassium chloride is used as an agricultural fertiliser under the name ‘muriate of potash’. Cesium is used in the manufacture of photoelectric cells.

#### Summary

 Group 1 metals are also called as alkali metals. These are the most reactive metals. They contain only one electron in its valence shell thus they form +1cations. The alkali metals are good conductors, and they have a shiny, silvery appearance. In flame tests, lithium forms a candy-apple red colour, while sodium produces a yellow flame and potassium a lilac flame. Chemical properties: They react with hydrogen to form metal hydrides. 2M + H2 → 2MH (Where M= Li, Na, K, Rb, Cs) They react with halogens to form alkali metal halide salts, such as NaCl. 2Na + Cl2 → 2NaCl They react with oxygen lithium forms oxides, sodium forms peroxides, and the other group 1 metals form superoxides. 4Li + O2 → 2Li2O (Lithium oxide) 2Na + O2 → Na2O2 (Sodium peroxide) M + O2 → MO2 Where M = K, Rb, Cs   Alkali metals react vigorously with water to produce hydroxide ions in solution, and hydrogen gas.  Applications: An alloy with lead is used to make engine parts, an aluminium-lithium alloy is used in airplane construction and a magnesium-lithium alloy is used to make armour plates. Lithium metal is used in some thermonuclear reactions and to construct various types of batteries. Sodium-lead alloy was used to produce organo-lead compounds such as tetraethyl lead, which was used as an anti-knock agent in automobile fuel.  Potassium has a variety of roles in biological systems.  Potassium chloride is used as an agricultural fertiliser under the name ‘muriate of potash’. Cesium is used in the manufacture of photoelectric cells.

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