A metal ‘M’ reacts with nitrogen gas to afford ‘M₃N’. ‘M₃N’ on heating at high temperature gives back ‘M’ and on reaction with water produces a gas ‘B’. Gas ‘B’ reacts with aqueous solution of CuSO₄ to form a deep blue compound. ‘M’ and ‘B’ respectively are :

The number of S = O and S − OH bonds present in peroxodisulphuric acid and pyrosulphuric acid respectively are :

The products obtained when chlorine gas reacts with cold and dilute aqueous NaOH are :

Aqueous solution of which salt will not contain ions with the electronic configuration 1s²2s²2p⁶3s²3p⁶ ?