Question

b] Two elements - one of which is a neutral gas and the other a monovalent metal
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Answer 1

Answer:

Neutral gas ----> O2  

    Monovalent metal ----> Na (with valency equal to 1)

Balanced equation is -

6Na  +  2O2 -----> 2Na​2O   +    Na2O2

Answer 2

Answer:

Neutral gas-Helium,Neon,Argon,Krypton,Xenon

Monovalent metals-Lithium,Sodium,Potassium,Rubidium,Caesium