All alkali metals dissolve in anhydrous liquid ammonia to give blue colour solution. It is the ammoniated electron which is responsible for the blue colour of the solution, and the electrical conducti

Question

All alkali metals dissolve in anhydrous liquid ammonia to give blue colour 
solution. It is the ammoniated electron which is responsible for the blue colour
of the solution, and the electrical conductivity is due to the ammoniated 
cation, [M(NH3)x]+ as well as the ammoniated electron, -, values of x and y 
depend on the extent of solvation by NH3. Dilute solutions are paramagnetic due 
to free ammoniated electrons.

Prashant Kotian · Accepted Answer

Correct answer: D. Step 1: When highly reactive metals are burned in air, they can react with atmospheric nitrogen to form metal nitrides. Lithium (Li) and alkaline earth metals (Mg, Ca) easily form nitrides (Li3N, Mg3N2, Ca3N2) due to high lattice energy stabilization. Step 2: Potassium (K) has a larger cationic size and lower lattice energy, which prevents it from reacting directly with nitrogen gas to form a stable nitride on burning in air. Step 3: Upon exposure to moisture, the nitrides of Li, Mg, and Ca hydrolyze to release ammonia gas (NH3), which has a characteristic sharp smell. Since Potassium does not form a nitride, it does not produce ammonia under these conditions. Thus, option (c) is correct.

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