Question:medium

The number of paramagnetic species among the following is ____B2,Li2,C2,C-2, O22--,O2+ and He2+

Updated On: Apr 13, 2026
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Correct Answer: 4

Solution and Explanation

To determine the number of paramagnetic species among B2, Li2, C2, C2-, O22-, O2+, and He2+, we need to analyze their electron configurations and look for unpaired electrons.

Step 1: Determine Electron Configuration
B2: Total electrons = 10. Configuration: (σ1s)2(σ*1s)2(σ2s)2(σ*2s)2(π2p)2. Two unpaired electrons → paramagnetic.
Li2: Total electrons = 6. Configuration: (σ1s)2(σ*1s)2(σ2s)2. All paired electrons → diamagnetic.
C2: Total electrons = 12. Configuration: (σ1s)2(σ*1s)2(σ2s)2(σ*2s)2(π2p)4. All paired electrons → diamagnetic.
C2-: Total electrons = 13. Configuration: (σ1s)2(σ*1s)2(σ2s)2(σ*2s)2(π2p)4(π*2p)1. One unpaired electron → paramagnetic.
O22-: Total electrons = 18. Configuration: (σ1s)2(σ*1s)2(σ2s)2(σ*2s)2(π2p)4(σ2p)2(π*2p)4. All paired electrons → diamagnetic.
O2+: Total electrons = 15. Configuration: (σ1s)2(σ*1s)2(σ2s)2(σ*2s)2(π2p)4(π*2p)3. One unpaired electron → paramagnetic.
He2+: Total electrons = 3. Configuration: (σ1s)2(σ*1s)1. One unpaired electron → paramagnetic.

Step 2: Count Paramagnetic Species
The paramagnetic species are B2, C2-, O2+, and He2+. Thus, there are 4 paramagnetic species.

Conclusion: The number of paramagnetic species is 4, which falls within the expected range of 4,4.

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