Reaction with non-metals

(i) These have high affinity for non-metals. Except carbon and nitrogen, they directly react with hydrogen, halogens, sulfur, phosphorus etc. to form corresponding compounds on heating.

                       300^oC

2Na + Cl₂ → 2NaCl ; 2K + Cl₂ → 2KCl

2Na + S → Na₂S; 2K + S → K₂S

3Na + P → Na₃P; 3K + P → K₃P

(ii) Li reacts, however directly with carbon and nitrogen to form carbides and nitrides.

2Li + 2C → LiC₂ ; 6Li + 2N₂ → 2 Li₃N

(iii) The nitrides of these metals on reaction with water give NH₃.

M₃N + 3H₂O → 3MOH + NH₃

Reaction with acidic hydrogen : Alkali metals react with acids and other compounds containing acidic hydrogen (i.e, H atom attached on F,O, N and triply bonded carbon atom, for example, HF, H₂O, ROH, RNH₂, CH ≡ CH) to liberate H₂ .

M + H₂O → MOH + 1/2 H₂; M + HX → MX + 1/2 H₂

M + ROH → ROH + 1/2 H₂; M + RNH₂ → RNHNa + 1/2 H₂