The compouds with the highest degree of covalency is :

Options

A. `NaCl`
B. `MgCl_(2)`
C. `AgCl`
D. `CsCl`

Answer

To determine which compound has the highest degree of covalency among the given options, we need to analyze the electropositivity of the metal and the electronegativity of chlorine, which is the common non-metal in all the compounds. The degree of covalency is higher when the difference between the electropositive element and the electronegative element is low.

### Step-by-Step Solution:

1. **Understanding Degree of Covalency**:
- The degree of covalency is influenced by the difference in electronegativity between the two elements in a compound. A smaller difference indicates a higher degree of covalency.

2. **Identify the Compounds**:
- The compounds given are likely to include sodium chloride (NaCl), cesium chloride (CsCl), magnesium chloride (MgCl2), and silver chloride (AgCl).

3. **Electronegativity of Chlorine**:
- Chlorine (Cl) has a relatively high electronegativity value, which is consistent across all compounds. Therefore, we will focus on the electropositivity of the metals.

4. **Electropositivity of Metals**:
- Sodium (Na): Alkali metal, highly electropositive.
- Cesium (Cs): Alkali metal, most electropositive in the periodic table.
- Magnesium (Mg): Alkaline earth metal, less electropositive than alkali metals.
- Silver (Ag): A d-block element, not very electropositive compared to the others.

5. **Comparing Electropositivity**:
- The electropositivity of the metals can be ranked as follows:
- Cs > Na > Mg > Ag
- Since cesium is the most electropositive, it will have the highest difference with chlorine, leading to lower covalency.

6. **Evaluating the Compounds**:
- For NaCl: Difference in electronegativity is moderate.
- For CsCl: Highest difference due to high electropositivity of Cs.
- For MgCl2: Moderate difference, but Mg is less electropositive than Cs and Na.
- For AgCl: Silver has the lowest electropositivity, resulting in the smallest difference with chlorine.

7. **Conclusion**:
- Since AgCl has the smallest difference between the electropositivity of silver and the electronegativity of chlorine, it exhibits the highest degree of covalency among the given options.

### Final Answer:
The compound with the highest degree of covalency is **AgCl (Silver Chloride)**.