The number of paramagnetic species among the following is ___________. B , Li , C , C , O , O and He — Chemical Bonding Chemistry Question

💡 Solution & Explanation

**Step 1: Identify the species** The species are: B, Li, C, C₂, O, O₂, and He **Step 2: Recall the paramagnetic criterion** A species is paramagnetic if it has unpaired electrons. Use electron configuration to count unpaired electrons. **Step 3: Analyze each species** - **B** (atomic number 5): 1s² 2s² 2p¹ → 1 unpaired electron → **Paramagnetic** - **Li** (atomic number 3): 1s² 2s¹ → 1 unpaired electron → **Paramagnetic** - **C** (atomic number 6): 1s² 2s² 2p² → 2 unpaired electrons → **Paramagnetic** - **C₂** (molecular): σ1s² σ*1s² σ2s² σ*2s² π2p⁴ → 2 unpaired electrons in π2p orbitals → **Paramagnetic** - **O** (atomic number 8): 1s² 2s² 2p⁴ → 2 unpaired electrons → **Paramagnetic** - **O₂** (molecular): π2p⁴ configuration → 2 unpaired electrons (π*2p²) → **Paramagnetic** - **He** (atomic number 2): 1s² → No unpaired electrons → **Diamagnetic** **Step 4: Count paramagnetic species** Paramagnetic species: B, Li, C, C₂, O, O₂ = 6 species... Wait, let me reconsider C₂ with proper MO theory: C₂ has configuration (σ1s)²(σ*1s)²(σ2s)²(σ*2s)²(π2p)⁴, meaning all electrons are paired → **Diamagnetic** **Revised count:** B, Li, C, O, O₂ = 5 species... Rechecking: including atomic C separately gives B, Li