The ion with large number of lone pairs on the halogen

Options

A. `ClO^(-)`
B. `ClO_(2)`
C. `CIO_(3)^(-)`
D. `CIO_(4)^(-)`

Answer

To determine which ion has the largest number of lone pairs on the halogen (Cl), let's analyze each option systematically.

### Step 1: Understand the Valence Electrons of Chlorine
Chlorine (Cl) has an atomic number of 17, which means it has 7 valence electrons (the configuration is 2, 8, 7).

**Hint:** Remember that the number of valence electrons is crucial for determining the bonding and lone pairs in molecules.

### Step 2: Analyze Each Ion
We will analyze the given ions one by one to find out how many lone pairs are present on the chlorine atom in each case.

#### Option A: ClO⁻
1. Chlorine has 7 valence electrons.
2. Oxygen typically has 6 valence electrons. In ClO⁻, there is one oxygen atom.
3. When Cl bonds with O, it forms one bond with O.
4. After forming the bond, the remaining electrons are calculated as follows:
- 7 (initial) - 1 (bond with O) = 6 electrons left.
5. These 6 electrons can be arranged into lone pairs:
- 6 electrons = 3 lone pairs.

**Lone pairs in ClO⁻ = 3**

#### Option B: ClO₂⁻
1. Chlorine still has 7 valence electrons.
2. In ClO₂⁻, there are two oxygen atoms.
3. Chlorine can form two bonds (one with each oxygen).
4. After bonding:
- 7 (initial) - 2 (bonds with O) = 5 electrons left.
5. These 5 electrons can be arranged into lone pairs:
- 5 electrons = 2 lone pairs and 1 single electron.

**Lone pairs in ClO₂⁻ = 2**

#### Option C: ClO₃⁻
1. Chlorine has 7 valence electrons.
2. In ClO₃⁻, there are three oxygen atoms.
3. Chlorine can form three bonds (one with each oxygen).
4. After bonding:
- 7 (initial) - 3 (bonds with O) = 4 electrons left.
5. These 4 electrons can be arranged into lone pairs:
- 4 electrons = 2 lone pairs.

**Lone pairs in ClO₃⁻ = 1**

#### Option D: ClO₄⁻
1. Chlorine has 7 valence electrons.
2. In ClO₄⁻, there are four oxygen atoms.
3. Chlorine can form four bonds (one with each oxygen).
4. After bonding:
- 7 (initial) - 4 (bonds with O) = 3 electrons left.
5. These 3 electrons can be arranged into lone pairs:
- 3 electrons = 1 lone pair.

**Lone pairs in ClO₄⁻ = 0**

### Step 3: Compare the Lone Pairs
Now we compare the number of lone pairs from each ion:
- ClO⁻: 3 lone pairs
- ClO₂⁻: 2 lone pairs
- ClO₃⁻: 1 lone pair
- ClO₄⁻: 0 lone pairs

### Conclusion
The ion with the largest number of lone pairs on the halogen (Cl) is **ClO⁻**, which has **3 lone pairs**.

**Final Answer:** Option A (ClO⁻) has the largest number of lone pairs on the halogen.

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