Pick out among the following, species isoelectronic with `CO_(2)`.

Options

A. `N_(3)^(-)`
B. `CNO^(-)`
C. `NCN^(2-)`
D. All of these

Explanation

To determine which species are isoelectronic with CO2, we need to follow these steps:

### Step 1: Calculate the number of electrons in CO2
- Carbon (C) has an atomic number of 6, so it has 6 electrons.
- Oxygen (O) has an atomic number of 8, and since there are 2 oxygen atoms in CO2, we multiply by 2: 8 × 2 = 16 electrons.
- Total number of electrons in CO2 = 6 (from C) + 16 (from 2 O) = 22 electrons.

### Step 2: Calculate the number of electrons in each given species
1. **For N3-**:
- Nitrogen (N) has an atomic number of 7, and there are 3 nitrogen atoms: 7 × 3 = 21 electrons.
- Since it has a -3 charge, we add 3 electrons: 21 + 3 = 24 electrons.

2. **For CNO-**:
- Carbon (C) has 6 electrons, Nitrogen (N) has 7 electrons, and Oxygen (O) has 8 electrons.
- Total = 6 (C) + 7 (N) + 8 (O) = 21 electrons.
- Since it has a -1 charge, we add 1 electron: 21 + 1 = 22 electrons.

3. **For N-C-N 2-**:
- Each nitrogen (N) has 7 electrons, and there are 2 nitrogen atoms: 7 × 2 = 14 electrons.
- Carbon (C) has 6 electrons.
- Total = 14 (from 2 N) + 6 (from C) = 20 electrons.
- Since it has a -2 charge, we add 2 electrons: 20 + 2 = 22 electrons.

### Step 3: Compare the total number of electrons
- CO2 has 22 electrons.
- N3- has 24 electrons (not isoelectronic).
- CNO- has 22 electrons (isoelectronic).
- N-C-N 2- has 22 electrons (isoelectronic).

### Conclusion
The species that are isoelectronic with CO2 are CNO- and N-C-N 2-.

### Summary of Isoelectronic Species
- CO2: 22 electrons
- CNO-: 22 electrons (isoelectronic)
- N-C-N 2-: 22 electrons (isoelectronic)

### Final Answer
The species isoelectronic with CO2 are CNO- and N-C-N 2-.

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