Question

Which one of the following shows maximum paramagnetic character?

• A. ${\left[Fe{\left(CN\right)}_6\right]}^{3-}$
• B. ${\left[Fe{\left(CN\right)}_6\right]}^{4-}$
• C. ${\left[Cr{\left(H_{2}O\right)}_6\right]}^{3+}$
• D. ${\left[Cu{\left(H_{2}O\right)}_6\right]}^{2+}$

Answer 1

The correct option is A ${\left[Fe{\left(CN\right)}_6\right]}^{3-}$

(i) $\left[Fe\right(CN{)}_6{]}^{3-}$

Here, oxidation state of $Fe=+3$

Electronic configuration of $Fe$ (ground state) $=\left[Ar\right]3d^{6}4s^2$

Electronic configuration of $Fe$ (excited state) $=\left[Ar\right]3d^{5}4s^0$

Number of unpaired electrons $=5$

(ii) $\left[Fe\right(CN{)}_6{]}^{4-}$

Here, oxidation state of $Fe=+2$

Electronic configuration of $Fe$ (ground state) $=\left[Ar\right]3d^{6}4s^2$

Electronic configuration of $Fe$ (excited state) $=\left[Ar\right]3d^{6}4s^0$

Number of unpaired electrons $=4$

(iii) $\left[Cr\right(H_{2}O{)}_6{]}^{3+}$

Here, oxidation state of $Cr=+3$

Electronic configuration of $C{r}^{3+}=\left[Ar\right]3d^{3}4s^0$

Number of unpaired electrons $=3$

(iv) $\left[Cu\right(H_{2}O{)}_6{]}^{2+}$

Here, oxidation state of $Cu=+2$

Electronic configuration of $C{u}^{2+}=\left[Ar\right]3d^{9}4s^0$

Number of unpaired electrons $=1$

A number of unpaired electrons present is directly proportional to a paramagnetic character.

So, $\left[Fe\right(CN{)}_6{]}^{3-}$ has maximum paramagnetic character.