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