Trends in M3+/M2+ Standard Electrode Potentials
1. Introduction to Standard Electrode Potential
The standard electrode potential (E°) for the M3+/M2+ system represents the tendency of a metal
ion (M3+) to gain one electron and get reduced to its M2+ state. It is measured in volts (V) relative to
the standard hydrogen electrode (SHE). A more positive E° value indicates a greater tendency for
reduction, while a more negative value indicates a greater tendency for oxidation.
2. Factors Affecting M3+/M2+ Electrode Potentials
- **Ionization Enthalpy**: Higher ionization energies make the formation of M3+ less favorable,
affecting E° values.
- **Hydration Enthalpy**: More hydration energy stabilizes the M3+ ion, increasing its reduction
potential.
- **Lattice Energy**: Stronger lattice energy favors the formation of M3+ ions in solid-state
compounds.
- **Electronic Configuration**: Half-filled and fully filled d-orbitals impact stability and reduction
potential.
3. Trends in the First Series of Transition Metals
In the 3d transition series (Sc to Zn), M3+/M2+ electrode potentials vary due to a combination of
ionization energy, hydration enthalpy, and electronic configuration.
- **Scandium (Sc)**: Strongly positive E° as Sc3+ is highly stable.
- **Titanium (Ti) to Manganese (Mn)**: Moderate E° values, with Mn3+ being less stable.
- **Iron (Fe) and Cobalt (Co)**: Fe3+ is more stable than Fe2+, leading to a positive E°.
- **Copper (Cu) and Zinc (Zn)**: Cu3+ and Zn3+ are highly unstable, so M3+/M2+ potentials are not
commonly considered.
4. Anomalous Behavior of Iron
Iron shows an interesting trend where Fe3+ is more stable in aqueous solutions due to its higher
hydration enthalpy. This makes the Fe3+/Fe2+ standard electrode potential more positive compared
to other transition metals.
5. Applications of Standard Electrode Potentials
- Used in predicting redox reactions and metal reactivity.
- Important in designing electrochemical cells and batteries.
1. Introduction to Standard Electrode Potential
The standard electrode potential (E°) for the M3+/M2+ system represents the tendency of a metal
ion (M3+) to gain one electron and get reduced to its M2+ state. It is measured in volts (V) relative to
the standard hydrogen electrode (SHE). A more positive E° value indicates a greater tendency for
reduction, while a more negative value indicates a greater tendency for oxidation.
2. Factors Affecting M3+/M2+ Electrode Potentials
- **Ionization Enthalpy**: Higher ionization energies make the formation of M3+ less favorable,
affecting E° values.
- **Hydration Enthalpy**: More hydration energy stabilizes the M3+ ion, increasing its reduction
potential.
- **Lattice Energy**: Stronger lattice energy favors the formation of M3+ ions in solid-state
compounds.
- **Electronic Configuration**: Half-filled and fully filled d-orbitals impact stability and reduction
potential.
3. Trends in the First Series of Transition Metals
In the 3d transition series (Sc to Zn), M3+/M2+ electrode potentials vary due to a combination of
ionization energy, hydration enthalpy, and electronic configuration.
- **Scandium (Sc)**: Strongly positive E° as Sc3+ is highly stable.
- **Titanium (Ti) to Manganese (Mn)**: Moderate E° values, with Mn3+ being less stable.
- **Iron (Fe) and Cobalt (Co)**: Fe3+ is more stable than Fe2+, leading to a positive E°.
- **Copper (Cu) and Zinc (Zn)**: Cu3+ and Zn3+ are highly unstable, so M3+/M2+ potentials are not
commonly considered.
4. Anomalous Behavior of Iron
Iron shows an interesting trend where Fe3+ is more stable in aqueous solutions due to its higher
hydration enthalpy. This makes the Fe3+/Fe2+ standard electrode potential more positive compared
to other transition metals.
5. Applications of Standard Electrode Potentials
- Used in predicting redox reactions and metal reactivity.
- Important in designing electrochemical cells and batteries.
