The number of unpaired electrons responsible for the paramagnetic nature of the following complex species are…

🧠 Count Unpaired Electrons in Each

🗺️ Evaluate

| Complex | Metal/d-config | Field | Spin | Configuration | Unpaired | |---|---|---|---|---|---| | $[\mathrm{Fe(CN)_6}]^{3-}$ | Fe(III) d⁵ | strong (CN⁻) | LS | $t_{2g}^5 e_g^0$ | 1 | | $[\mathrm{FeF_6}]^{3-}$ | Fe(III) d⁵ | weak (F⁻) | HS | $t_{2g}^3 e_g^2$ | 5 | | $[\mathrm{CoF_6}]^{3-}$ | Co(III) d⁶ | weak (F⁻) | HS | $t_{2g}^4 e_g^2$ | 4 | | $[\mathrm{Mn(CN)_6}]^{3-}$ | Mn(III) d⁴ | strong (CN⁻) | LS | $t_{2g}^4 e_g^0$ | 2 |

Sequence: 1, 5, 4, 2.

⚡ LS d⁴/d⁵/d⁶ Unpaired Counts

| d-config | LS unpaired | HS unpaired | |---|---|---| | d⁴ | 2 ($t_{2g}^4$) | 4 ($t_{2g}^3 e_g^1$) | | d⁵ | 1 ($t_{2g}^5$) | 5 ($t_{2g}^3 e_g^2$) | | d⁶ | 0 ($t_{2g}^6$) | 4 ($t_{2g}^4 e_g^2$) |

⚠️ Co(III) Almost Always LS (Except with F⁻ and H₂O)

Co(III) has unusually high pairing tendency. Only F⁻ and H₂O are weak enough to give HS Co(III).

$\boxed{\text{Answer: (1) 1, 5, 4, 2}}$