Question

Which one of the following species responds to an external magnetic field?

• A. ${\left[Fe{\left(H_{2}O\right)}_6\right]}^{3+}$
• B. ${\left[Co(CN{)}_6\right]}^{3-}$
• C. $\left[Ni(Co{)}_4\right]$
• D. ${\left[Ni(CN{)}_4\right]}^{2-}$

Answer 1

Answer: (A)

1. ${\left[Fe{\left(H_{2}O\right)}_6\right]}^{3+}$
$F{e}^{3+}:[Ar]3d^5$
Hybridisation: $s{p}^3{d}^2$
Magnetic nature: Paramagnetic (so this complex response to external magnetic field)
2. ${\left[Ni(CN{)}_4\right]}^{2-}$
$N{i}^{2+}:[Ar]3d^8$
Hybridisation: $ds{p}^2$
Magnetic nature: diamagnetic
3. ${\left[Co(CN{)}_6\right]}^{3-}$
$C{o}^{3+}:[Ar]3d^6$
Hybridisation: $d^{2}s{p}^3$
Magnetic nature: diamagnetic
4. $\left[Ni(CO{)}_4\right]$
$Ni:[Ar]3d^{8}4s^2$
Hybridisation : $s{p}^3$
Magnetic nature : diamagnetic