Which of the following is iso-electronic pair ?

Options

A. `ICl_(2),ClO_(2)`
B. `BrO_(2)^(-),BrF_(2)^(+)`
C. `ClO_(2),Brf`
D. `CN^(-),O_(3)`

Explanation

To determine which of the given pairs is an isoelectronic pair, we need to count the total number of electrons in each species. Isoelectronic pairs have the same number of electrons. Let's analyze the pairs step by step.

### Step 1: Analyze ICl2 and ClO2
1. **ICl2**:
- Iodine (I) has 53 electrons.
- Each Chlorine (Cl) has 17 electrons, and there are 2 Cl atoms.
- Total electrons in ICl2 = 53 (from I) + 2 × 17 (from Cl) = 53 + 34 = 87 electrons.

2. **ClO2**:
- Each Chlorine (Cl) has 17 electrons.
- Each Oxygen (O) has 8 electrons, and there are 2 O atoms.
- Total electrons in ClO2 = 17 + 2 × 8 = 17 + 16 = 33 electrons.

**Conclusion**: ICl2 (87 electrons) and ClO2 (33 electrons) are not isoelectronic.

### Step 2: Analyze BrO2- and BrF2+
1. **BrO2-**:
- Bromine (Br) has 35 electrons.
- Each Oxygen (O) has 8 electrons, and there are 2 O atoms.
- The negative charge adds 1 electron.
- Total electrons in BrO2- = 35 + 2 × 8 + 1 = 35 + 16 + 1 = 52 electrons.

2. **BrF2+**:
- Bromine (Br) has 35 electrons.
- Each Fluorine (F) has 9 electrons, and there are 2 F atoms.
- The positive charge subtracts 1 electron.
- Total electrons in BrF2+ = 35 + 2 × 9 - 1 = 35 + 18 - 1 = 52 electrons.

**Conclusion**: BrO2- (52 electrons) and BrF2+ (52 electrons) are isoelectronic.

### Step 3: Analyze ClO2 and BrF
1. **ClO2**:
- As calculated before, ClO2 has 33 electrons.

2. **BrF**:
- Bromine (Br) has 35 electrons.
- Fluorine (F) has 9 electrons.
- Total electrons in BrF = 35 + 9 = 44 electrons.

**Conclusion**: ClO2 (33 electrons) and BrF (44 electrons) are not isoelectronic.

### Step 4: Analyze CN- and O3
1. **CN-**:
- Carbon (C) has 6 electrons.
- Nitrogen (N) has 7 electrons.
- The negative charge adds 1 electron.
- Total electrons in CN- = 6 + 7 + 1 = 14 electrons.

2. **O3**:
- Each Oxygen (O) has 8 electrons, and there are 3 O atoms.
- Total electrons in O3 = 3 × 8 = 24 electrons.

**Conclusion**: CN- (14 electrons) and O3 (24 electrons) are not isoelectronic.

### Final Conclusion
The only pair that is isoelectronic is **BrO2- and BrF2+**, both having 52 electrons.

### Answer: The correct option is B (BrO2- and BrF2+).

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