Question

Among [Ni(CO)₄], [NiCl₄]²⁻, [Co(NH₃)₄Cl₂]Cl, Na₃[CoF₆], Na₂O₂ and CsO₂, the total number of paramagnetic compounds is ______.

Options

• 2

• 3

• 4

• 5

Answer 1

Among [Ni(CO)₄], [NiCl₄]²⁻, [Co(NH₃)₄Cl₂]Cl, Na₃[CoF₆], Na₂O₂ and CsO₂, the total number of paramagnetic compounds is 3.

Explanation:

1. [Ni(CO)₄] → CO is a strong field ligand → low-spin d⁸ → diamagnetic
2. [NiCl₄]²⁻ → Cl⁻ is weak field → high-spin d⁸ → paramagnetic
3. [Co(NH₃)₄Cl₂]Cl → Co³⁺ with NH₃ (moderate field) → low-spin d⁶ → diamagnetic
4. Na₃[CoF₆] → F⁻ is weak field → high-spin d⁶ → paramagnetic
5. Na₂O₂ → peroxide → all paired → diamagnetic
6. CsO₂ → superoxide → 1 unpaired electron → paramagnetic

Paramagnetic compounds: [NiCl₄]²⁻, Na₃[CoF₆], CsO₂ → 3 compounds