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Chemical Properties of Alkali Metals - 1 - (Concept)

Chemical Properties of Alkali Metals : The alkali metals are highly reactive due to their large size and low ionization enthalpy. The reactivity of these metals increases down the group.

  • Reactivity towards air: The alkali metals tarnish in dry air due to the formation of their oxides which in turn react with
    moisture to form hydroxides. They burn vigorously in oxygen forming oxides.
  • Reactivity towards water: The alkali metals react with water to form hydroxide and dihydrogen.
    2M + 2H_{2}O\rightarrow 2M^{+}+2OH^{-}+H_{2}
  • Reactivity towards dihydrogen: The alkali metals react with dihydrogen at about 673K (lithium at 1073K) to form hydrides. All the alkali metal hydrides are ionic solids with high melting points.
  • Reactivity towards halogens : The alkali metals readily react vigorously with halogens to form ionic halides, M+X- .
    However, lithium halides are somewhat covalent.
  • Reducing nature: The alkali metals are strong reducing agents, lithium being the most and sodium the least powerful
  • Solutions in liquid ammonia: The alkali metals dissolve in liquid ammonia giving deep blue solutions which are conducting in nature.The blue colour of the solution is due to the ammoniated electron which absorbs energy in the visible region of light and thus imparts blue colour to the solution.
Exam Chapter
MHT-CET S - Block Elements (Alkali and Alkaline Earth Metals)
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