Least ionic compound among the following is

Options

A. NaCl
B. KCl
C. Csl
D. LiI

Explanation

To determine the least ionic compound among the given options, we need to analyze the ionic and covalent character of the bonds in the compounds. The key factors influencing the ionic and covalent character are the sizes of the cation and anion, as well as their charges.

### Step-by-Step Solution:

1. **Understand Ionic vs. Covalent Character**:
- Ionic compounds are formed from the transfer of electrons from one atom to another, resulting in the formation of cations and anions.
- Covalent compounds involve the sharing of electrons.
- A compound can have both ionic and covalent character, and we want to find the one with the least ionic character (or the most covalent character).

2. **Use Fajans' Rules**:
- Fajans' rules help predict the degree of covalent character in ionic compounds.
- According to these rules, a large anion and a small cation will favor covalent character due to polarization.
- The polarization occurs when the small cation's positive charge distorts the electron cloud of the large anion.

3. **Identify the Compounds**:
- List the compounds given in the question. For example, let’s say the options are: NaCl, KBr, LiI, and CsCl.

4. **Compare Anion Sizes**:
- Among the halides, as we go down the group in the periodic table, the size of the anion increases.
- For example, I- (iodide) is larger than Br- (bromide), which is larger than Cl- (chloride).

5. **Compare Cation Sizes**:
- In the alkali metals, the size of the cation increases as we go down the group.
- Li+ is smaller than Na+, which is smaller than K+, and so on.

6. **Analyze Each Compound**:
- For NaCl: Na+ (small cation) and Cl- (medium-sized anion).
- For KBr: K+ (medium cation) and Br- (medium-sized anion).
- For LiI: Li+ (smallest cation) and I- (largest anion).
- For CsCl: Cs+ (largest cation) and Cl- (medium-sized anion).

7. **Determine the Least Ionic Compound**:
- The compound with the smallest cation and the largest anion will have the most covalent character.
- Comparing LiI (small cation Li+ and large anion I-) with the other compounds, it shows the highest covalent character.
- Therefore, LiI is the least ionic compound among the given options.

### Final Answer:
The least ionic compound among the given options is **LiI**.