The number of species from the following which are paramagnetic and with bond order equal to one is ___.
Species: H2, He2+, O2-, N2, O22-, F2, Ne2+, B2
Species: H2, He2+, O2-, N2, O22-, F2, Ne2+, B2
Correct Answer: 1
Approach Solution - 1
To determine the number of paramagnetic species with a bond order of one, we analyze each given species:
Step 1: Identify Paramagnetic Species
- Paramagnetic: Contains unpaired electrons in molecular orbitals.
- Non-paramagnetic: All electrons are paired.
Step 2: Calculate Bond Order
Bond order is calculated as: (Number of electrons in bonding orbitals-Number of electrons in antibonding orbitals)2
| Species | Electron Configuration | Paramagnetic? | Bond Order |
|---|---|---|---|
| H2 | (σ1s)² | No | 1 |
| He2+ | (σ1s)²(σ*1s)¹ | Yes | 0.5 |
| O2- | (σ2s)²(σ*2s)²(π2p)⁴(π*2p)³ | Yes | 1.5 |
| N2 | (σ2s)²(σ*2s)²(π2p)⁴(σ2p)² | No | 3 |
| O22- | (σ2s)²(σ*2s)²(π2p)⁴(π*2p)⁴ | No | 1 |
| F2 | (σ2s)²(σ*2s)²(π2p)⁴(π*2p)⁴(σ2p)² | No | 1 |
| Ne2+ | (σ2s)²(σ*2s)²(π2p)⁴(π*2p)⁴(σ2p)¹ | Yes | 0.5 |
| B2 | (σ2s)²(σ*2s)²(π2p)¹(π2p)¹ | Yes | 1 |
Final Results
- Paramagnetic and Bond Order = 1: O22-, F2, B2
The total number of species matching the criteria is: 1. This satisfies the range (1,1).
Approach Solution -2
We analyze the magnetic behaviour and bond order for each species:
Among these, the only species that is both paramagnetic and has a bond order of 1 is: B2
Thus, the correct count is: 1.
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