To determine which group represents a collection of isoelectronic species, we need to find out how many electrons each species has in the given options. Isoelectronic species are those that have the same number of electrons.
### Step-by-Step Solution:
1. **Identify the species in each option**: We will analyze each option provided in the question to determine the number of electrons in each species.
2. **Calculate the number of electrons for each species**:
- **Option 1: NO, CN⁻, N₂, O²⁻**
- **NO**: Nitrogen (N) has 7 electrons, Oxygen (O) has 8 electrons. Total = 7 + 8 = 15 electrons.
- **CN⁻**: Carbon (C) has 6 electrons, Nitrogen (N) has 7 electrons, and the negative charge adds 1 electron. Total = 6 + 7 + 1 = 14 electrons.
- **N₂**: Two Nitrogens = 7 + 7 = 14 electrons.
- **O²⁻**: Two Oxygens = 8 + 8 + 2 (for the two negative charges) = 18 electrons.
- **Conclusion**: Different electron counts (15, 14, 14, 18) → Not isoelectronic.
3. **Option 2: NO⁺, C₂²⁻, O²⁻, CO**
- **NO⁺**: 7 (N) + 8 (O) - 1 (for the positive charge) = 14 electrons.
- **C₂²⁻**: 6 (C) + 6 (C) + 2 (for the two negative charges) = 14 electrons.
- **O²⁻**: 8 (O) + 8 (O) + 2 (for the two negative charges) = 18 electrons.
- **CO**: 6 (C) + 8 (O) = 14 electrons.
- **Conclusion**: Counts are 14, 14, 18, 14 → Not all the same → Not isoelectronic.
4. **Option 3: N₂, C₂²⁻, CO, NO**
- **N₂**: 7 + 7 = 14 electrons.
- **C₂²⁻**: 6 + 6 + 2 = 14 electrons.
- **CO**: 6 + 8 = 14 electrons.
- **NO**: 7 + 8 = 15 electrons.
- **Conclusion**: Counts are 14, 14, 14, 15 → Not all the same → Not isoelectronic.
5. **Option 4: CO, NO⁺, C₂²⁻, CN⁻**
- **CO**: 6 (C) + 8 (O) = 14 electrons.
- **NO⁺**: 7 (N) + 8 (O) - 1 = 14 electrons.
- **C₂²⁻**: 6 + 6 + 2 = 14 electrons.
- **CN⁻**: 6 (C) + 7 (N) + 1 = 14 electrons.
- **Conclusion**: All species have 14 electrons → This group is isoelectronic.
### Final Answer:
The collection of isoelectronic species is found in **Option 4: CO, NO⁺, C₂²⁻, CN⁻**.
