The ion which is iso-electronic with CO is:

Options

A. `CN^(-)`
B. `O_(2)^(-)`
C. `N_(2)^(+)`
D. `O_(2)^(+)`

Explanation

To determine which ion is iso-electronic with CO (carbon monoxide), we need to follow these steps:

### Step 1: Understand the concept of isoelectronic species
Isoelectronic species are atoms, ions, or molecules that have the same number of electrons. Therefore, we need to find the total number of electrons in CO.

### Step 2: Calculate the number of electrons in CO
- Carbon (C) has 6 electrons.
- Oxygen (O) has 8 electrons.
- Total electrons in CO = 6 (from C) + 8 (from O) = 14 electrons.

### Step 3: Analyze the given options
We need to calculate the number of electrons for each of the given ions to find out which one has 14 electrons.

1. **CN⁻ (Cyanide ion)**:
- Carbon (C) has 6 electrons.
- Nitrogen (N) has 7 electrons.
- The negative charge (⁻) indicates there is one additional electron.
- Total electrons in CN⁻ = 6 (from C) + 7 (from N) + 1 (extra electron) = 14 electrons.

2. **O₂⁻ (Superoxide ion)**:
- Each oxygen (O) has 8 electrons.
- There are two oxygen atoms, so 8 + 8 = 16 electrons.
- The negative charge (⁻) indicates one additional electron.
- Total electrons in O₂⁻ = 16 + 1 = 17 electrons.

3. **N₂⁺ (Nitrogen ion)**:
- Each nitrogen (N) has 7 electrons.
- There are two nitrogen atoms, so 7 + 7 = 14 electrons.
- The positive charge (⁺) indicates one less electron.
- Total electrons in N₂⁺ = 14 - 1 = 13 electrons.

4. **O₂⁺ (Oxygen ion)**:
- Each oxygen (O) has 8 electrons.
- There are two oxygen atoms, so 8 + 8 = 16 electrons.
- The positive charge (⁺) indicates one less electron.
- Total electrons in O₂⁺ = 16 - 1 = 15 electrons.

### Step 4: Compare the total electrons
- CN⁻ has 14 electrons (iso-electronic with CO).
- O₂⁻ has 17 electrons (not iso-electronic).
- N₂⁺ has 13 electrons (not iso-electronic).
- O₂⁺ has 15 electrons (not iso-electronic).

### Conclusion
The ion that is iso-electronic with CO is **CN⁻**.

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