To determine the number of paramagnetic species among the given molecules: O₂, CO, N₂, C₂, CsO₂, BaO₂, and CO₂, we need to analyze the number of unpaired electrons in each species. A species is considered paramagnetic if it has one or more unpaired electrons.
### Step-by-Step Solution:
1. **Identify the number of valence electrons for each molecule:**
- **O₂:** Each oxygen atom has 6 valence electrons. Therefore, O₂ has \(6 \times 2 = 12\) valence electrons.
- **CO:** Carbon has 4 valence electrons and oxygen has 6. Thus, CO has \(4 + 6 = 10\) valence electrons.
- **N₂:** Each nitrogen atom has 5 valence electrons. Therefore, N₂ has \(5 \times 2 = 10\) valence electrons.
- **C₂:** Each carbon atom has 4 valence electrons. Thus, C₂ has \(4 \times 2 = 8\) valence electrons.
- **CsO₂:** Cesium (Cs) has 1 valence electron and O₂ has 12 (as calculated above). Therefore, CsO₂ has \(1 + 12 = 13\) valence electrons.
- **BaO₂:** Barium (Ba) has 2 valence electrons and O₂ has 12. Thus, BaO₂ has \(2 + 12 = 14\) valence electrons.
- **CO₂:** Carbon has 4 valence electrons and each oxygen has 6. Therefore, CO₂ has \(4 + 6 \times 2 = 16\) valence electrons.
2. **Determine the pairing of electrons:**
- **O₂ (12 electrons):** All electrons can be paired, so it is **diamagnetic**.
- **CO (10 electrons):** All electrons can be paired, so it is **diamagnetic**.
- **N₂ (10 electrons):** All electrons can be paired, so it is **diamagnetic**.
- **C₂ (8 electrons):** All electrons can be paired, so it is **diamagnetic**.
- **CsO₂ (13 electrons):** One unpaired electron, so it is **paramagnetic**.
- **BaO₂ (14 electrons):** All electrons can be paired, so it is **diamagnetic**.
- **CO₂ (16 electrons):** All electrons can be paired, so it is **diamagnetic**.
3. **Count the number of paramagnetic species:**
- From the analysis, only **CsO₂** is paramagnetic.
### Final Answer:
The number of paramagnetic species among the given molecules is **1** (only CsO₂).
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