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 solve the question regarding the largest contribution in the Born-Haber cycle for the formation of solid common salt (NaCl), we can follow these steps:

### 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 from the constituent elements in their standard states.

2. **Identify the Components Involved in NaCl Formation**:
- Sodium (Na) in solid form.
- Chlorine (Cl) in diatomic form (Cl₂).
- The formation of NaCl involves several steps: sublimation of sodium, ionization of sodium, dissociation of chlorine, electron affinity of chlorine, and the lattice energy of NaCl.

3. **List the Relevant Energies**:
- **Sublimation of Sodium**: Converts solid Na to gaseous Na (ΔH_sublimation = +108 kJ/mol).
- **Ionization Energy of Sodium**: Converts gaseous Na to Na⁺ (ΔH_ionization = +496 kJ/mol).
- **Dissociation of Chlorine**: Converts Cl₂ to 2 Cl (ΔH_dissociation = +122 kJ/mol).
- **Electron Affinity of Chlorine**: Converts Cl to Cl⁻ (ΔH_electron affinity = -349 kJ/mol).
- **Lattice Energy of NaCl**: Energy released when Na⁺ and Cl⁻ combine to form NaCl (ΔH_lattice = -788 kJ/mol).

4. **Analyze Each Contribution**:
- The sublimation and ionization energies are positive contributions (endothermic).
- The dissociation energy is also a positive contribution (endothermic).
- The electron affinity is a negative contribution (exothermic).
- The lattice energy is a significant negative contribution (exothermic).

5. **Determine the Largest Contribution**:
- Among all these energies, the lattice energy (ΔH_lattice = -788 kJ/mol) is the largest in magnitude (most negative) and thus has the largest contribution to the overall energy change in the formation of NaCl.

6. **Conclusion**:
Therefore, the largest contribution in the Born-Haber cycle for the formation of solid common salt (NaCl) comes from the lattice energy.

### Final Answer:
The largest contribution comes from the lattice energy.