Uses of NaHCO₃
(i) It is used in fire extinguisher
(ii) It is mild antiseptic for skin infections
(iii) It is used as antacid

Alkali metals and alkaline earth metals are most electropositive due to low ionization ethalpy therefore they form ionic hydrides. e.g. NaH, KH and CaH₂

The unusual properties of lithium as compared to other alkali metals is due to its exceptionally small size of atom and its ion and its high polarising power.

Due to small size, lithium does not form alums

Lithium cannot be used in making photoelectric cells because out of all the alkali metals it has highest ionization energy and thus cannot emit electrons when exposed to light.

Smaller the size (internuclear distance), more is the value of Lattice enthalpy since internuclear distance is expected to be least in the LiF.

Sodium is highly reactive but less reactive than potassium, that's why it is found to be more useful than potassium.
Therefore, sodium is used
I. as a coolant in nuclear reactor.
II. in the manufacture of tetraethyl lead, an anti-knock additive for petrol.
4 C₂H₅Cl + 4 Na - Pb \(\longrightarrow \) (C₂H₅)₄ Pb + 3 Pb + 4 NaCl
III. in sodium vapour discharge lamps.
IV. as a laboratory reagent for organic analysis.
Na + NH₃ \(\longrightarrow \) NaNH₂ + H₂

I. Alkali metals are  strong reducing agents, hence cannot be extracted by reduction of their oxides and other compounds.
II. Being highly positive in nature it is not possible to displace them from their salt solutions by any other elements.
III. Alkali metals cannot be obtained by the electrolysis of the aqueous solution of their salts because H₂ is liberated at cathode instead of alkali metal.
That's why alkali metals are prepared by electrolysis of their fused chloride.
NaCl  \(\underrightarrow { Fusion } \) Na⁺ + Cl^-
During electrolysis
At anode, 2 Cl^- \(\longrightarrow \) Cl₂ + 2 e^-
At cathode, 2 Na⁺ + 2 e^-  \(\longrightarrow \)  2 Na

The stability of peroxide or superoxide increases as the size of metal ion increases i.e.
 KO₂  <  RbO₂  <  CsO₂
The reactivity of alkali metals toward oxygen to form different oxides is due to string positive field around each alkali metal cation. Li⁺ is the smallest. it does not allow O2^-  ion to react with O2 further. Na⁺ is larger than Li, its positive field is weaker than Li⁺.
It cannot prevent the conversion of O^2- into O₂^2-. The large ions such as K⁺, Rb⁺ and Cs⁺ permit  O₂^2- ion to react with O2 forming superoxide ion O^2-
\({ O }_{ 2 }^{ 2- }  \overset { \frac { 1 }{ 2 } { O }_{ 2 } }{ \longrightarrow  } O^{2-}   \overset { { O }_{ 2 } }{ \longrightarrow  } 2 { O }_{ 2 }^{ - }\)
Furthermore, increased stability of the peroxide or superoxide with increase in the size of metal ion is due to the stabilisation of large anions by larger cations through lattice energy effect.

Aluminium possesses high electrical conductivity. Therefore, it is used in making transmission cables. Further on weight to weight basis conductivity of aluminium is twice as Cu.

Because aluminium reacts with water and oxygen (dissolved in ) to form a thin layer of toxic aluminium oxide on the surface of utensils.
2Al(s) + O₂(g) + H₂O(l)\(\rightarrow\)Al₂O₃(s) + H₂(g)

Basicity of oxides The oxides of the alkali and alkaline earth metals dissolves in water to form basic hydroxides. The alkaline earth metal hydroxides are however less basic and less stable than alkali metal hydrooxides.