Trends in M2+/M Standard Electrode Potentials
1. Introduction to Standard Electrode Potential
The standard electrode potential (E°) for the M2+/M system represents the tendency of a metal ion
(M2+) to gain two electrons and get reduced to its metallic form (M). 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 M2+/M Electrode Potentials
- **Ionization Enthalpy**: Higher ionization energy makes it harder to remove electrons, lowering the
reduction potential.
- **Hydration Enthalpy**: More hydration energy stabilizes the M2+ ion, making reduction less
favorable.
- **Lattice Energy**: Stronger metallic bonds make it harder for the metal to dissolve into ions,
affecting E° values.
- **Electronic Configuration**: Stable half-filled or fully filled d-orbitals impact reduction tendencies.
3. Trends in the First Series of Transition Metals
In the 3d transition series (Sc to Zn), M2+/M electrode potentials do not show a smooth trend due to
the interplay of ionization energy, hydration enthalpy, and lattice energy.
- **Scandium (Sc)**: Highly negative E° due to strong ionization energy.
- **Titanium (Ti) to Manganese (Mn)**: Slightly increasing values due to stable 3d configurations.
- **Iron (Fe) to Copper (Cu)**: More positive E° values due to higher hydration enthalpy.
- **Zinc (Zn)**: High positive value, as Zn2+ is highly stable with a fully filled 3d10 configuration.
4. Anomalous Behavior of Copper
Copper has a highly positive standard electrode potential (E° = +0.34 V), meaning Cu2+ prefers to
remain in solution rather than get reduced to Cu(s). This is due to its high ionization energy and
favorable hydration enthalpy. Unlike other first-row transition metals, copper does not readily react
with acids to release H2 gas.
5. Applications of Standard Electrode Potentials
- Used in electrochemical series to predict redox reactions.
- Helps in designing batteries and corrosion-resistant materials.
- Essential in understanding metal extraction and refining processes.
1. Introduction to Standard Electrode Potential
The standard electrode potential (E°) for the M2+/M system represents the tendency of a metal ion
(M2+) to gain two electrons and get reduced to its metallic form (M). 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 M2+/M Electrode Potentials
- **Ionization Enthalpy**: Higher ionization energy makes it harder to remove electrons, lowering the
reduction potential.
- **Hydration Enthalpy**: More hydration energy stabilizes the M2+ ion, making reduction less
favorable.
- **Lattice Energy**: Stronger metallic bonds make it harder for the metal to dissolve into ions,
affecting E° values.
- **Electronic Configuration**: Stable half-filled or fully filled d-orbitals impact reduction tendencies.
3. Trends in the First Series of Transition Metals
In the 3d transition series (Sc to Zn), M2+/M electrode potentials do not show a smooth trend due to
the interplay of ionization energy, hydration enthalpy, and lattice energy.
- **Scandium (Sc)**: Highly negative E° due to strong ionization energy.
- **Titanium (Ti) to Manganese (Mn)**: Slightly increasing values due to stable 3d configurations.
- **Iron (Fe) to Copper (Cu)**: More positive E° values due to higher hydration enthalpy.
- **Zinc (Zn)**: High positive value, as Zn2+ is highly stable with a fully filled 3d10 configuration.
4. Anomalous Behavior of Copper
Copper has a highly positive standard electrode potential (E° = +0.34 V), meaning Cu2+ prefers to
remain in solution rather than get reduced to Cu(s). This is due to its high ionization energy and
favorable hydration enthalpy. Unlike other first-row transition metals, copper does not readily react
with acids to release H2 gas.
5. Applications of Standard Electrode Potentials
- Used in electrochemical series to predict redox reactions.
- Helps in designing batteries and corrosion-resistant materials.
- Essential in understanding metal extraction and refining processes.
