Question

The $d$-electron configurations of $C{r}^{2+},M{n}^{2+},F{e}^{2+}$ and $C{o}^{2+}$ are $d^4,d^5,d^6$ and $d^7$ respectively. Which one of the following will exhibit the lowest paramagnetic behaviour? (Atomic no. $Cr=24,Mn=25,Fe=26,Co=27$ ).

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

Answer 1

Answer: (A)

$\therefore$ Since $C{o}^{2+}$ has lowest no. of unpaired electrons hence lowest paramagnetic behaviour is shown by ${\left[Co{\left(H_{2}O\right)}_6\right]}^{2+}$