V2+ has d3 configuration of which all the 3 are unpaired electrons, Cr2+ has d4 configuration. On low spin the 4 electrons are arranged as one pair and 2 unpaired electrons, Ru3+ has d5 configuration. In low spin the 5 electrons are arranged as2 pairs ard 1 electron remain unpaired Fe2+ has d6 configuration. In low spin complex all the six electrons are paired so no unpaired electrons