Question

Which one of the following will show paramagnetism
corresponding to 2 unpaired electrons?
(Atomic numbers : Ni = 28, Fe = 26)
(a) [FeF₆]³⁻ (b) [NiCl₄]²⁻
(c) [Fe (CN)₆]³⁻ (d) [Ni (CN)₄]²⁻

Answer 1

(B) [NiCl4]2- shows the paramagnetism.

• strong paramagnetism decrease with the rise in temperature.

• weak paramagnetism is independent of temperature.

Answer 2

Coordination compound which will show paramagnetism corresponding to 2 unpaired electrons is :

1. [FeF₆]³⁻,

• Atomic no. of Fe = 26

• Oxidation number in coordination compound = +3

• Electronic configuration of Fe3+

= 1s2 2s2 2p6 3s2 3p6 3d5

• No of unpaired electrons = 5

• Also weak field ion is present, hence pairing is not possible.

2. [NiCl₄]²⁻

• Atomic no. of Ni = 28

• Oxidation number in coordination compound = +2

• Electronic configuration of Ni2+

= 1s2 2s2 2p6 3s2 3p6 3d8

• No of unpaired electrons = 2

• Again weak field ion is present, hence pairing is not possible.

• It is paramagnetic in nature.

• We also got our answer. i.e option (b)