Question

The number of species from the following which are paramagnetic and with bond order equal to one is ___.
Species: H₂, He₂⁺, O₂^-, N₂, O₂^2-, F₂, Ne₂⁺, B₂

Answer 1

Correct Answer: 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: O₂^2-, F₂, B₂

The total number of species matching the criteria is: 1. This satisfies the range (1,1).

Answer 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.