• # question_answer Which of the following is diamagnetic?     JEE Main  Online Paper (Held On 22 April 2013) A) $[\operatorname{F}e{{({{\operatorname{CN}}_{6}})}^{3-}}$                    B)  ${{[\operatorname{Co}(\operatorname{O}\operatorname{X})]}^{3-}}$C)  ${{[\operatorname{Fe}{{\operatorname{F}}_{6}}]}^{3-}}$                        D)  ${{[\operatorname{Co}{{\operatorname{F}}_{6}}]}^{3-}}$

${{[Fe{{(CN)}_{6}}]}^{3-}}$has magnetic moment of a single unpaired electron whereas ${{[Fe{{F}_{6}}]}^{3-}}$ has  a magnetic moment of five unpaired electrons. ${{[Co{{F}_{6}}]}^{3-}}$is paramagnetic with four unpaired electrons while ${{[Co{{({{C}_{2}}{{O}_{4}})}_{3}}]}^{3}}$ is diamagnetic. This anomaly is explained by valence bond theory in terms of formation of inner and outer orbital coordination entities. ${{[Co{{({{C}_{2}}{{O}_{4}})}_{3}}]}^{3-}}$is an inner orbital complexes having ${{d}^{2}}s{{p}^{3}}$hybridization.