Final answer:
Non-metallic half reactions involve the transfer of electrons and may require water or hydrogen ions to balance oxygen or hydrogen atoms, ensuring conservation of atoms and charge balance.
Step-by-step explanation:
When there is no metal in the half reactions of a redox process, it typically indicates that the reaction involves the transfer of electrons between non-metallic elements or ions. For example, in the reduction half-reaction where nitrate is reduced to nitric oxide, no metal is involved. Similarly, in the oxidation half-reaction of hydrogen ions to hydrogen gas (2H+ + 2e- → H2), there is no metal present. These half-reactions are essential to ensure the charge balance and the conservation of atoms during the overall reaction. In cases where there are oxygen or hydrogen atoms, water molecules (H2O) or hydrogen ions (H+) might be added to balance the reaction.