Q56. Among $\mathrm { VO } _ { 2 } ^ { + } , \mathrm { MnO } _ { 4 } ^ { - }$and $\mathrm { Cr } _ { 2 } \mathrm { O } _ { 7 } ^ { 2 - }$, the spin-only magnetic moment value of the species with least oxidising ability is $\_\_\_\_$ BM (Nearest integer). (Given atomic member $\mathrm { V } = 23 , \mathrm { Mn } = 25 , \mathrm { Cr } = 24$ )