Alkali Metals

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Alkali Metals Introduction Alkali metals refer to six elements belonging to the Group IA of the long form of the Modern Periodic Table, viz. Lithium (Li), Sodium (Na), Potassium (K), Rubidium (Rb), Cesium (Cs) and Francium (Fr). Fr is a radioactive element. These elements are called so because they form strongly alkaline oxides and hydroxides. Electronic Configuration of Alkali Metals Each of the alkali metals has one electron in their outermost (valence) shell, which is just outside an inert gas core. Element Atomic No. Electronic Structure Valence Shell Electron Li 3 He core, 2s1 i.e. 1s22s1 2s1 Na 11 Ne core, 3s1 i.e. 1s22s22p63s1 3s1 K 19 Ar core, 4s1 i.e.…show more content…
3. Reaction with H2O – formation of hydroxide: * All the alkali metals react vigorously with H2O to form hydrogen gas and the metallic hydroxide and, for this reason, must be stored under kerosene, coated with paraffin, or protected in some other fashion. The activity increases as the atomic weight increases. 2M + 2H2O → 2MOH + H2 * All the alkali metal hydroxides are alkaline in aqueous solution with the alkalinity naturally increasing on going down the group. 4. Reaction with H2 – formation of hydride: The alkali metals, on heating, react quite readily with hydrogen to give white crystalline salt-like hydrides. The tendency to form the hydrides decreases from Li to Cs. 2M + H2 → 2MH 5. Reaction with halogens – formation of halides: Alkali metals combine directly with halogens to form halides. The ease with which the alkali metals form halides increases from Li to Cs. 2M + X2 → 2MX X = F, Cl, Br, I 6. Reaction with N2: * Only Li reacts readily with N2 at room temperature to form lithium nitride (Li3N), which decomposes in water to form ammonia and lithium hydroxide. 6Li + N2 → 2Li3N * Other alkali metals
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