The group reagent H2S in the presence of NH4OH is used for the precipitation of Group IV cations in qualitative analysis.
Among the given ions, Mn2+ belongs to Group IV and is precipitated as MnS.
Pb2+ and Cu2+ belong to Group II and are precipitated by H2S in an acidic medium.
Fe3+ belongs to Group III and is precipitated as Fe(OH)3 by NH4OH in the presence of NH4Cl.
The metal corresponding to the precipitated ion is Manganese (Mn).
The electronic configuration of Mn is [Ar]3d54s2. By losing all its valence electrons, it can exhibit a maximum oxidation state of +7 (for example, in KMnO4).
Answer: +7