The ion that is isoelectronic with `CO` is

Options

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

Answer

To determine which ion is isoelectronic with carbon monoxide (CO), we first need to find out how many electrons are present in the CO molecule.

### Step-by-Step Solution:

1. **Determine the number of electrons in CO:**
- Carbon (C) has an atomic number of 6, which means it has 6 electrons.
- Oxygen (O) has an atomic number of 8, which means it has 8 electrons.
- Therefore, the total number of electrons in CO is:
\[ 6 \, (\text{from C}) + 8 \, (\text{from O}) = 14 \, \text{electrons} \]

2. **Evaluate the options given:**
- **Option 1: CN⁻**
- Carbon (C) has 6 electrons.
- Nitrogen (N) has 7 electrons.
- The CN⁻ ion has one additional electron due to the negative charge:
\[ 6 \, (\text{from C}) + 7 \, (\text{from N}) + 1 \, (\text{extra electron}) = 14 \, \text{electrons} \]
- **Option 2: O₂⁻**
- Each oxygen atom has 8 electrons, and there are two oxygen atoms:
\[ 8 + 8 = 16 \, \text{electrons} \]
- With one extra electron due to the negative charge:
\[ 16 + 1 = 17 \, \text{electrons} \]
- **Option 3: O₂⁻ (same as option 2)**
- This will also have 17 electrons.
- **Option 4: N₂⁺**
- Each nitrogen atom has 7 electrons, and there are two nitrogen atoms:
\[ 7 + 7 = 14 \, \text{electrons} \]
- With a positive charge, one electron is lost:
\[ 14 - 1 = 13 \, \text{electrons} \]

3. **Conclusion:**
- The only ion that has 14 electrons, which is the same as CO, is CN⁻.
- Therefore, the ion that is isoelectronic with CO is **CN⁻**.

### Final Answer:
The ion that is isoelectronic with CO is **CN⁻**.