Q. 14.2( 81 Votes )
What are the common physical and chemical features of alkali metals?
Alkali metals are first group metals in periodic table.
Common physical properties of alkali metals are:
1) Alkali metals have one electron in there valence shell so are ready to give it easily to complete their octet.
2) They exhibit +1 oxidation state in their compounds.
3) They impart colours to flames. This is because the heat from flame excites the electron present in outer orbital and when it comes back it gives out light in visible spectrum.
4) Alkali metals are soft and can be easily cut. Sodium (Na) can be cut easily by knife.
5) They have low melting points as metallic bond present in metals is quite weak.
6) They show photoelectric effect. When metals like Cs and K are exposed to sunlight, they lose electrons.
Common Chemical properties of alkali metals are:
1) Due to only one electron in their outer shell, they can donate it easily. So they are quite reactive. Sodium(Na) is stored in kerosene instead of water.
2) They react to water to form hydroxides which are generally basic in nature.
2M + H2O → 2M+ + 2OH- + H2
3) They react with dihydrogen to form metal hydrides.
2m + H2→ 2M+H-
4) They are strong reducing agents and as you go down the group their reducing power increases.
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