question_answer

Which one of the following complexes is paramagnetic in nature?

A)  \[{{[Zn{{(N{{H}_{3}})}_{4}}]}^{2+}}\]                     

B)  \[{{(Co{{(N{{H}_{3}})}_{6}}]}^{3+}}\]

C)  \[{{[Ni{{({{H}_{2}}O)}_{6}}]}^{2+}}\]                      

D)  \[{{[Ni{{(CN)}_{4}}]}^{2-}}\]

Correct Answer: C

Solution :

                 \[{{[Zn{{(N{{H}_{3}})}_{4}}]}^{2+}}\] \[Z{{n}^{2+}}={{d}^{10}}\] \[\therefore \,{{[Zn{{(N{{H}_{3}})}_{6}}]}^{3+}}\] is diamagnetic.  \[{{[Co{{(N{{H}_{3}})}_{6}}]}^{3+}}\] \[C{{o}^{3+}}={{d}^{8}}\] As \[N{{H}_{3}}\] is strong field ligand, due to which pairing of electron occur. \[\therefore \] After pairing                 \[\therefore \,{{[Co{{(N{{H}_{3}})}_{6}}]}^{3+}}\] is also diamagnetic                  \[{{[Ni{{({{H}_{2}}O)}_{6}}]}^{2+}}\]                                 As \[{{H}_{2}}O\] is a weak field ligand, due to which pairing of electron did not occur.                 \[\therefore \] It is a paramagnetic in nature.  \[Ni{{(CN)}_{4}}{{]}^{2-}}\] \[N{{i}^{2+}}={{d}^{8}}\]       CN is strong field ligand, due to which pairing of electron takes place . Hence \[{{[Ni{{(CN)}_{4}}]}^{2-}}\] is also diamagnetic in nature.