Paramagnetic Species with Bond Order Equal to One

The number of species from the following which are paramagnetic and with bond order equal to one is ________.

H₂, He₂⁺, O₂⁺, N₂²⁻, O₂²⁻, F₂, Ne₂⁺, B₂

Correct Answer: 1

Explanation

A species must satisfy both conditions:

• It must be paramagnetic (at least one unpaired electron).
• Its bond order must be exactly equal to one.

• H₂ → Bond order = 1 but diamagnetic ✘
• He₂⁺ → Bond order = 0.5 ✘
• O₂⁺ → Bond order = 2.5 ✘
• N₂²⁻ → Bond order = 2 ✘
• O₂²⁻ → Bond order = 1 but diamagnetic ✘
• F₂ → Bond order = 1 but diamagnetic ✘
• Ne₂⁺ → Bond order = 0.5 ✘
• B₂ → Bond order = 1 and paramagnetic ✔

Hence, only one species (B₂) satisfies both conditions.

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