Atomic number of Cr , Fe and Co are 24, 26 and 27 respectively. Which of the following inner orbital octahedral complexes are paramagnetic?

Step-by-step solution

[ Cr ( CN )₆ ]³⁻ Oxidation state of Cr : x+(-1) 6=-3 aligned x & =+3 Cr & =[ Ar ] 4 s^1 3 d^5 Cr ³⁺ & =[ Ar ] 4 s^0 3 d^3 aligned Since, CN is a strong field ligand, it will cause pairing of electrons in Cr ³⁺ , So, there is one unpaired electron in 3 d -orbital of Cr ³⁺ which makes the compound [ Cr ( CN )₆ ]³⁻ paramagnetic.