In the Born-Haber cycle for the formation of solid common salt (NaCl), the largest contribution comes from :

Options

A. the low ionization potential of Na
B. the high electron affinity of Cl
C. the low `DeltaH_("vap")` of Na(s)
D. the lattice energy

Answer

To determine the largest contribution in the Born-Haber cycle for the formation of solid common salt (NaCl), we need to analyze the options provided in the context of the Born-Haber cycle.

### Step-by-Step Solution:

1. **Understanding the Born-Haber Cycle**:
The Born-Haber cycle is a thermodynamic cycle that relates the lattice energy of an ionic solid to the enthalpy changes involved in its formation. It includes steps such as sublimation, ionization, dissociation, electron affinity, and lattice formation.

2. **Analyzing the Options**:
- **Option 1: Low ionization potential of Na**:
The ionization energy of Na is +496 kJ/mol. While this value is significant, it is not the largest contribution in the cycle.

- **Option 2: High electron affinity of Cl**:
The electron affinity of Cl is -349 kJ/mol. This value indicates that energy is released when Cl gains an electron, but it is still not the largest contribution.

- **Option 3: Low ΔH vaporization of Na**:
The heat of vaporization of Na is +108 kJ/mol. This value is relatively low compared to the lattice energy and does not contribute significantly to the overall energy change.

- **Option 4: Lattice energy**:
The lattice energy (U) is -788 kJ/mol. This is the energy released when gaseous ions combine to form a solid ionic compound. It is a large negative value, indicating a strong attraction between the ions in the solid state.

3. **Conclusion**:
Among all the contributions analyzed, the lattice energy has the largest magnitude and is the most significant contributor to the overall energy change in the formation of NaCl. Therefore, the correct answer is **Option 4: Lattice energy**.

### Final Answer:
The largest contribution in the Born-Haber cycle for the formation of solid common salt (NaCl) comes from the **lattice energy**.

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