Final answer:
In the redox reaction: Pb2+ + NH4+ to Pb + NO3−, lead (Pb) is reduced while nitrogen (N) is the element being oxidized.
Step-by-step explanation:
To determine which element is being oxidized in the given redox reaction, we need to look at the changes in oxidation states of the elements involved in the reaction. The reaction given is Pb2+(aq) + NH4+(aq) → Pb(s) + NO3−(aq). In this reaction, lead (Pb) goes from Pb2+ to Pb(s). It gains electrons and goes from a +2 oxidation state to a 0 oxidation state. This is a reduction process. Since oxidation and reduction always occur together, we know that the element that loses electrons (and is thereby oxidized) must be nitrogen (N) from the NH4+ ion, which goes to the NO3− ion.